Session Deletion Notification/Disable TextView when Appropriate

Users who are not the session creator are now notified that the session
will be deleted when the session creator chooses "Delete Session" after
leaving.  After clicking 'OK', the user will then be disconnected.

The TextView is now also disabled before connecting to a session.
Connecting to a session succesfully causes the textview to be enabled,
and disconnecting from the session disables it again.