Improvements on BetaSeries

- Lookup from BetaSeries search if not on tvdb : it will use BetaSeries search function to find show. This way will cause more delay than the first one, because we would certainly have more than one result, but it's still a good fix to get subs from this service
- Sort by language preferences : considere user preferences

I didn't want to do these 2 improvements by one lonely commit, but I messed up with my local branches :-/ ...