Exists and Update operation on Scopes, Rights and Roles

[sandorfr]

Add Exists and update role operation to make it possible to update/maintain the scope hierarchy using the provisioning client and without modifying the database directly.

[sandorfr]

going through the current code base I have the feeling that most Create Operation are now Upsert (in which case they should be renamed :)). If that's the case it could satisfy that need entirely.