Add Database Migration Support

Add database migration support to Barbican.

As the data model for Barbican changes over time, migration scripts should be generated and then applied to the existing database schema, to bring the schema up to the latest version of the schema needed.

This blueprint should also begin documenting guidance on how to perform migrations in a manner that accommodates a rolled out means to deploy Barbican nodes, with new-version node rolled out along side current-version nodes.