support updating objectClasses for a User

This PR does a few things:

- moves existing deactivatedUid and new objectClass meta-data to a common implementation meta-data HashMap.
- implementation meta-data is not observed for object equality
- updates objectClasses based on current state of User object
- always updates objectClass on object update
I added in the remove based on this earlier discussion:

https://github.com/GlobalTechnology/idm-user-management/pull/30#issuecomment-66651541

I'm removing it for the scenario that someone has all the cru person attributes removed