[new] You can now easily check & manipulate bitfield attributes via Object::bit_state()
[dev] Use the new Object::bit_state in some methods of User class
[new] Check for presence of mailbox or mailUser on the current user ( requires some attributes to be loaded - check API documentation )
[dev] Add checks if current user is already mail-enabled to User::new_mailbox() and User::mail_enable()
[dev] Make sure that the user's Exchange attributes are reset when mail-enabling
[dev] Add some inline documentation