pom.xml: Externalise Gerrit version variable Change-Id: I3e72c293644862f503f8141e4a87d41c01e11e79
Global ref-database interface for use with Gerrit Code Review.
Enables the de-coupling between Gerrit, the multi-site plugin and the different implementations of a globally shared ref-database.
The design for a global ref-db interface for Gerrit has been posted to the Gerrit Code Review project for review.