This adds a notification type for shaderfx so the properties editor can be properly notified to redraw. Another possible solution would be to also redraw the shaderfx tab with a ND_MODIFIER update, but this solution allows us to avoid some unecessary redraws too. There were no existing cases of ND_OBJECT | NC_MODIFIER updates, so those cases were removed from buttons_area_listener. Differential Revision: https://developer.blender.org/D8159