Common model integration

As for now we're using only Entity and Repository clases from the Common Model component. We need to reuse also User entity and migrations. To make all these things consistent we should define our own derivative of Common Model User class which will include all the additional info we now have in our User class. Fleway migrations are to be chained: Commons Model migrations first, then ours. Use flyway beans dependency to archive it.

It's still questionable if we can adopt ACL-related services from common model component, please also investigate it too.