[mythtv] Schema Update for tmdb3.py

[Raymond Wagner]

While it's not certain whether or not we're actually in feature freeze 
at the moment, I've just pushed a schema bump to force everyone running 
0.27 and currently using the tmdb.py grabber to the tmdb3.py grabber. As 
mentioned in the commit, the API that tmdb.py uses to access metadata 
will be shut down on September 15th, so this is a necessary change.