[database] - add setting for hiding watched movies/episodes in recently added lists

This is the c++ alternative to #5745

Not sure if i got the intention right. Not even sure why i joined that party tbh.

This basically adds 2 settings "Hide watched movies in recently added list." and "Hide watched episodes in recently added list." to the videos->Library section which does exactly that (and yes - this setting influences all recently added lists for movies/episodes - not only the ones on the home screen).

@MartijnKaijser let me know if this hits the feature request (i was kinda sick to read it completely and have the feeling that the bikeshedding didn't happen yet - so lets start it).

I* as its a feature... (this is btw not even compile tested yet ...)