In order to allow MBS-12107, as a prerequisite we must create the dbmirror2 schema in production as well as on mirror servers (so they have a place to import the changes).

This only introduces a new, yet-unused schema ("dbmirror2") to the database with some associated functions.  As it does not modify any existing parts of the schema, it should have no effect on mirrors.

The changes for mirror servers (which are also applied on the master) can be found at https://github.com/metabrainz/dbmirror2/blob/master/ReplicationSetup.sql

The changes for the production master (or any instance that generates replication changes) can be found at https://github.com/metabrainz/dbmirror2/blob/master/MasterSetup.sql