quick_frontend, primitivus: notifications refactoring

replaced old "alerts" system by a more generic one which use listeners and can activate callbacks on notification click.

frontends/src/quick_frontend/quick_chat.py

@@ -340,15 +340,6 @@ class QuickChat(quick_widgets.QuickWidget):
         """
         raise NotImplementedError
 
-    def notify(self, contact="somebody", msg=""):
-        """Notify the user of a new message if the frontend doesn't have the focus.
-
-        @param contact (unicode): contact who wrote to the users
-        @param msg (unicode): the message that has been received
-        """
-        # FIXME: not called anymore after refactoring
-        raise NotImplemented
-
     def printDayChange(self, day):
         """Display the day on a new line.