#1 presence notification

[Michael Salcher]

At the moment sink automatically requests and grants
presence notification authorization. This works fine as
long as we don't remove a buddy and add this buddy
later on. Example: Buddy A has Buddy B on his buddy
list and the vis versa. Both have presence notification
enabled. Buddy A removes Buddy B from his buddy list.
That means that Buddy B cannot see if Buddy A is online
anymore. If Buddy A puts Buddy B back on his buddy
list, Buddy A can see if Buddy B is online but not the
other way around. A fix would be to enable Buddy B to
request presence notification authorization.