updated copyright dates, added release statement to ChangeLog

updated release version in configure.ac

hammer: fixed building on debian buster

[#734,!422] Fixed filename in contribute.dox

    devel/contribute.dox - text had old file name, added " or:"

[#734,!422] contributors guide renamed to CONTRIBUTING.md

[#740,!427] Updated ChangeLog entry

[#740,!427] Added ChangeLog entry

[#740,!427] Addressed review comments

    src/lib/database/Makefile.am
    src/lib/dhcpsrv/Makefile.am
    src/lib/http/Makefile.am
    src/lib/stats/Makefile.am
    - Set age to 0 for reflect need to recompile:

    src/lib/process/Makefile.am
    - added interface, bump current and age

[#740,!427] Bumping library version numbers for 1.6.0-beta2

libkea_asiodns      -> no changes
libkea_asiolink     -> 7:2:0 (rule #3)
libkea_cc           -> 9:0:1 (rule #4,#5) Added BaseStampedElement class
libkea_cfgclient    -> 7:1:0 (rule #3) internal changes
libkea_cql          -> no changes
libkea_cryptolink   -> no changes
libkea_database     -> 3:0:1 (rule #4,#5) Support for Server objects
libkea_dhcp         -> 13:0:0 (rule #4) OptionDefContainer declaration changes
libkea_dhcp_ddns    -> no changes
libkea_dhcpsrv      -> 16:0:1 (rule #4, #5) ConfigBackendDHCPv* support for Server objects
libkea_dns          -> no changes
libkea_eval         -> 10:1:0 (rule #3)
libkea_exceptions   -> no changes
libkea_hooks        -> 7.3.0, bumped KEA_HOOKS_VERSION to 10
libkea_http         -> 6:0:1 (rule #4, #5) close_callback handler parameter added
libkea_log          -> no changes
libkea_mysql        -> 1:1:0 (rule #3) schema version was bumped
libkea_pgsql        -> 0:1:0 (rule #3) schema version was bumped
libkea_process      -> 4:1:0 (rule #3)
libkea_stats        -> 3:0:1 (rule #4,#5) Support for multiple data points per stat
libkea_threads      -> no changes
libkea_util_io      -> no changes, a Copyright year was updated
libkea_util         -> no changes, a typo in a comment was fixed
libkea_yang         -> 1:3:0 (rule #3)

[#741,!428] Fixed doxygen errors

Fixed two minor doxygen errors:
    src/hooks/dhcp/high_availability/ha_service.h
    src/lib/http/client.h

[#643,!421] Added ChangeLog entry for #643.

[#643,!421] Addressed review comments.

- Include "server-tags" instead of"server-tag" in the remote-network[46]-get
- Removed unnecessary escapes in the hooks-cb-cmds.
- Regenerated api.xml.

[#643,!421] Regenerated api.xml.

[#643,!421] Corrected JSON syntax in some of the API commands.

[#643,!421] Small corrections in the DHCPv4 CB text.

[#643,!421] Added a warning about misconfigurations when using server tags.

[#643,!421] Revised "Kea Configuration Backend" section.

[#643,!421] Added a note about shareable and non-shareable config in DHCP.

[#643,!421] Extended cb_cmds hook documentation with the server tags.

Each command description now comes with more examples of server tags usage
and the doc explicitly states when the server-tags are mandaotry and when
they must not be included in the command.

[#643,!421] Written section "Configuration Sharing and Server Tags".

[#643,!421] Removed the server tags from the CB limitations in the doc.

[#643,!421] Corrected introductory part of the cb_cmds doc.

Previously we used "server-tag" parameter in metadata, now we have
"server-tags" list.

[#643,!421] Editorial corrections in the cb_cmds docs for servers.

[#643,!421] Added documentation for the cb_cmds/server commands.

[#643,!421] Regenerated api.xml.

[#643,!421] Fixed JSON in remote-global-parameterX-del.json.

[#643,!421] Updated API docs for subnets management with tags.

[#643,!421] Updated API docs for shared networks managemen with tags.

[#643,!421] Updated API doc for remote global option commands.

[#643,!421] Updated API doc for option definitions.

[#643,!421] Updated API docs for global parameters setting.

[#643,!421] Created API docs for remote-server* commands.

[738-kea4-crash-when-remote-network4-del-command-is-issued-with-subnets-action-delete] Added ChangeLog entry for delete embedded subnet fix

[738-kea4-crash-when-remote-network4-del-command-is-issued-with-subnets-action-delete] Addressed final comments

[738-kea4-crash-when-remote-network4-del-command-is-issued-with-subnets-action-delete] Addressed comments

[738-kea4-crash-when-remote-network4-del-command-is-issued-with-subnets-action-delete] Fixed: use only ANY

[737-remote-option-def4-get-all-return-incorrect-tag-when-option-definition-is-configured-with-all] Added ChangeLog entry for MySQL CB option def get*

[737-remote-option-def4-get-all-return-incorrect-tag-when-option-definition-is-configured-with-all] Fixed option def get all query

[208-finish-move-logging] Improved log message

[208-finish-move-logging] Two other cases...

[208-finish-move-logging] Addressed comment

[208-finish-move-logging] Fixed libprocess - need d2 unit tests

[73-fix-covery-CID-1442796] Added initialization to 0 to next_host_id_ field of CfgHost

[606-drop-packets-in-drop-class] Added ChangeLog entry for DROP class

[606-drop-packets-in-drop-class] Addressed final comments

[606-drop-packets-in-drop-class] Addressed minor comments (checkpoint before rebasing)

[606-drop-packets-in-drop-class] Added DROP class (including doc and unit tests)

[701-sanitizer-logic-is-wrong] Added unit tests

updated ChangeLog, AUTHORS and addressed formatting

Support for storing more than one sample

[712-cb_cmds-add-support-for-server-tags-in-the-shared-networks] Improved supported selector comments

[712-cb_cmds-add-support-for-server-tags-in-the-shared-networks] Aligned on #717

[712-cb_cmds-add-support-for-server-tags-in-the-shared-networks] Added a note about supported even not (yet) allowed selectors

[712-cb_cmds-add-support-for-server-tags-in-the-shared-networks] Finished CB tests

[712-cb_cmds-add-support-for-server-tags-in-the-shared-networks] Updated CB API description and test utils

[#717,!417] Added ChangeLog for #717.

[717-mysql_cb-extend-the-backend-with-the-ability-to-associate-the-subnets-with-the-server-tags] Fixed SubnetFetcher comments

[#717,!417] Corrected CB API selectors' descriptions.

[#717,!417] Changed "network" to "subnet" in mysql_cb subnet tests.

[#717,!417] Extended mysql_cb test to insert subnet when there is no server.

[#717,!417] Fixed comment in DHCPv6 CB API description.

[#717,!417] Methods updating options don't use server tags.

[717-mysql_cb-extend-the-backend-with-the-ability-to-associate-the-subnets-with-the-server-tags] Added missing spaces

[717-mysql_cb-extend-the-backend-with-the-ability-to-associate-the-subnets-with-the-server-tags] Removed spurious blank line

[717-mysql_cb-extend-the-backend-with-the-ability-to-associate-the-subnets-with-the-server-tags] spelling

[#717,!417] Corrected SubnetFetcher6 unit test.

[#717,!417] Documented selectors for globals and options.

[#717,!417] Documented server selectors allowed for subnets.

[#717,!417] Use ANY server selector when fetching subnets for shared net.

[#717,!417] Validate server selectors in subnet manipulations.

[#717,!417] Added support for deleting unassigned subnets.

[#717,!417] Added support to delete a subnet with ANY server selector.

[#717] Added tests for fetching all subnets with server tags.

[#717] Associate subnets with server tags.

[master] [perf] entry type added to Changelog

[576-cb-cmds-empty-value-for-next-server-parameter-is-accepted-which-causes-misconfiguration] Moved the body to .cc

[576-cb-cmds-empty-value-for-next-server-parameter-is-accepted-which-causes-misconfiguration] Moved ElementValue specialization and changed getGlobalProperty full specialization to overloading

[576-cb-cmds-empty-value-for-next-server-parameter-is-accepted-which-causes-misconfiguration] Specialized the getGlobalProperty template for Optional<IOAddress>

[576-cb-cmds-empty-value-for-next-server-parameter-is-accepted-which-causes-misconfiguration] Protected getSiaddr against global being empty string

[#716,!412] Added ChangeLog for #716.

[#716,!412] StampedElement stores server tags in a set rather that vector.

[#716,!412] Reject "any" keyword as a server tag.

[716-mysql_cb-extend-the-backend-with-the-ability-to-associate-the-shared-networks-with-the-server-tags] spelling

[#716,!412] Documented and tested server selection for shared networks.

Also fixed the code where it accepted unsupported selectors. Implemented
deleting the unassigned subnets.

[#716,!412] Addressed easy review comments.

- Use variable to hold mysql_insert_id in insertOption4/6 function.
- Use variable for timestamp binding in insertOption4/6 function
- Removed unused MYSQL_DELETE_OPTION_SERVER query
- Removed LAST_INSERT_ID from a query
- Unit test tries to insert shared network for non-existing server.

[716-mysql_cb-extend-the-backend-with-the-ability-to-associate-the-shared-networks-with-the-server-tags] Delete Option6 by network does not use the server selector

[716-mysql_cb-extend-the-backend-with-the-ability-to-associate-the-shared-networks-with-the-server-tags] Removing DELETE_OPTION4_SERVER

[#716,!412] Added support for unassigned networks addition/deletion.

[#716,!412] Multiple tags are returned with shared networks.

[#716,!412] It is now possible to delete shared network by tags.

Support added for: any server, explicit server, all servers.

[#716,!412] Added support for associating networks with servers.

[595-permission-problem-with-posgresql-read-only-unit-test] Added welcome message from Debian 10 vm

[595-permission-problem-with-posgresql-read-only-unit-test] Added alternate way to give SELECT permission for RO PostgreSQL unit tests

[#710,!408] Fixed invalid tabulations in test config backends impl.

[710-cb_cmds-add-support-for-server-tags-in-global-options] Addressed some comments

[710-cb_cmds-add-support-for-server-tags-in-global-options] Completed CB testutils

[630-cb-can-be-used-to-remove-mandatory-global-parameters] Added ChangeLog entry for default values of external config globals

[630-cb-can-be-used-to-remove-mandatory-global-parameters] Addressed comments

[630-cb-can-be-used-to-remove-mandatory-global-parameters] (checkpoint) Added applyDefaultsConfiguredGlobals

[533-response-to-remote-global-parameter4-set-is-incomplete] Updated remote-global-parameter[46]-set doc