groups :

-Use a method to get_shown_groups (possibly more work to do (special group attribute))
-Show contact only if contact.ask, not according to modified xep 0162 logic. (I don't get neither the xep
meaning, neither this modified logic, can you explain steve-e ?)
-Remove contact before we modify it req_sub(). Else we can't remove it because iter is not found.
-When removing a contact and we let him in see us (observer), manually set show to offline, so he is not set as
visible.
-Remove observer from observer group if we asked him auth (I mean before he answer). Xep 0162 say he is not an
observer then. Fix contact staying in observer group when we get auth later.
-Renaming groups seems fixed (it's an accident :p )

More work on group to follow