Move tv shows subtitle query to OpenSubtitle provider

I was working on the idea of create an alternative subtitle provider for spanish language 
(discussed here http://discuss.get-popcorn.com/t/better-quality-subtitles-for-spanish-language/417 )
 when i found the subtitles for TV Shows query is not managed by a provider but in a function in the database (?).

This patch moves the implementation to a proper provider.