Merge pull request #2012 in SNORT/snort3 from ~RUCOMBS/snort3:new_stuff to master

Merge pull request #2012 in SNORT/snort3 from ~RUCOMBS/snort3:new_stuff to master

Squashed commit of the following:

commit 442e97ad2054e74f008a9f800f1e99930e24e8af
Author: russ <rucombs@cisco.com>
Date:   Sat Feb 15 10:27:32 2020 -0500

    gtp_inspect: fix default port binding

    The default snort.lua had a port binding to type = 'gtp' which is a typo.
    The service is 'gtp' and the inspector is 'gtp_inspect'.  Due to a flaw in
    lookup, the inspector was being matched by service.  To avoid confusing type
    and service the lookups were separated.  However, we silenty covert the old
    type = 'gtp' bidings to type = 'gtp_inspect' until RC at which point this
    deprecated usage support will be removed.

commit 215bd1e4829550183ae36198a3764245a3669cba
Author: russ <rucombs@cisco.com>
Date:   Sat Feb 15 10:08:29 2020 -0500

    inspectors: ensure correct lookup by type, name, or service

commit db649915eddbf805d9f587dd985ec9bd254b4f37
Author: russ <rucombs@cisco.com>
Date:   Sat Feb 8 10:12:19 2020 -0500

    metadata: add --metadata-filter to load matching rules only

    Rule metadata is a comma separated list of name-value tokens, eg:
    metadata:impact_flag red,policy security-ips drop,ruleset community;
    --metadata-filter f will load only rules where f appears in one of
    the metadata tokens.  "policy security" and "security-ips" would
    both match the above example.  Rules that are filtered out are
    counted as "total rules not loaded" in the startup output.