rhbz1036435 - Upgrade liquibase to 3.x stream.

Upgrade xml schemas used.
Remove deprecated modify-table liquibase extension. Replace all of its uses with more recent replacement directives.
rhbz1036435 - Change trigger changelog id.

This is to force the new liquibase version to run them unconditionally.
Also remove referecnes to the deprecated liquibase extensions from the changelog files.
rhbz1036435 - Add comment with liquibase upgrade notice.
Merge pull request #308 from zanata/liquibase-3.x-upgrade

rhbz1036435: Upgrade liquibase to 3.x stream.