[#15,!11] Schema upgrades for Kea 1.5, now update subnet ids in existing host reserva...

[#15,!11] Schema upgrades for Kea 1.5, now update subnet ids in existing host reservations

src/bin/admin/tests/pgsql_tests.sh.in
src/bin/admin/tests/cql_tests.sh.in
src/bin/admin/tests/mysql_tests.sh.in
    Added functions that verify subnet id values are updated

src/share/database/scripts/cql/upgrade_2.0_to_3.0.sh.in
src/share/database/scripts/mysql/upgrade_6.0_to_7.0.sh.in
src/share/database/scripts/pgsql/upgrade_4.0_to_5.0.sh.in
    Added logic to update subnet id values in existing reservations
    and options