Commented Task: Move some logic out from Logged User into Account [2543]

Comments: Associated with changeset 42815: Version 0.9.7.0
- Refactor of the Friendship Controller, QueryExecutor and QueryGenerator
- Removed some Friendship function like lookup from LoggedUser
- Added some FriendshipController feature within the Account singleton
- Performed some renaming
- Added missing relationship properties
- Handling private accounts relationships instead of throwing exception
- IUser is now an IUserIdentifier but the Id, ScreenName and IdStr cannot be modified
- Added method overloads to simplify the access for developers