Revision 1443

* Thuban/UI/messages.py (MAP_REPLACED): New message.

* Thuban/UI/view.py (MapCanvas.SetMap): Issue MAP_REPLACED after
the new map has been assigned

* Thuban/UI/mainwindow.py (MainWindow.delegated_messages):
Delegate MAP_REPLACED to the canvas too

* Thuban/UI/classifier.py (Classifier.__init__): Subscribe to
MAP_REPLACED so that we can close the dialog if a new map is set.
(Classifier.unsubscribe_messages): Unsubscribe from MAP_REPLACED
(Classifier.map_replaced): Handle MAP_REPLACED by closing the
dialog