mod to provide On Deck TV episode

mod to provide On Deck TV episode rather than simply the first unwatched episode

Pros: matches On Deck feature from Plex, makes sloppy/disorderly libraries less of a penalty for users.
Cons: adds about 60% processing time to the fetch_tvshows_recommended method (about 0.12 seconds on my i5 laptop and about 5 seconds on my Raspberry Pi)