Revision 125

	* Thuban/UI/view.py: Keep the temporary bitmap used during drawing
	around to speed up most redraws:
	(MapCanvas.__init__): New instance variable bitmap which holds the
	bitmap
	(MapCanvas.do_redraw): Redraw self.bitmap if necessary. Use
	self.bitmap to draw.
	(MapCanvas.full_redraw): New method to force a full redraw
	including the bitmap
	(MapCanvas.SetMap): Subscribe full_redraw instead of redraw to
	make sure the bitmap is redrawn.
	(MapCanvas.projection_changed, MapCanvas.set_view_transform,
	MapCanvas.shape_selected): Call full_redraw instead of readraw to
	make sure the bitmap is redrawn.
	(MapCanvas.OnSize): New method to handle size events so that the
	bitmap can be redrawn.