update CBLView setMapBlock: to post kCBLDatabaseChangeNotification. this causes any live queries to be updated
CBLView now post as notification when the mapblock changes of an existing view. CBLLiveQuery now listens for this and updates itself accordingly. unit test included
Merge pull request #473 from mglasgow/bug-updateViewShouldUpdateLiveQueries

CBLLiveQuery will now refresh after the view's mapBlock is changed.

Fixes #471