- added loading spinner for images in FriendsMainFragment
- addedListener for the following situations: onFriendOnline, onFriendOffline, onFriendLeftGame and onFriendOnlineStatusChange.

- improved the loading of the application and the service: the service runns now totally independent from the app. If the user lauch the app and the service is already with an authenticated session that is the same as the session the user wants to start, it simply binds the service again and reuse the connection. It creates a new session otherwise.

- small bugfixes