Make the Watched Status reflect truly what's watched and what's not.

[ensapra]

Stremio Version
All versions

Is your feature request related to a problem? Please describe.
I'm mad that every time I watch an episode of a show it gets flagged as watched when it shouldn't. It's correct for movies, but I feel like a show should be considered in another way. With a filter to remove watched and not watched it could clean up the library while still serving as a place to see what I have used it for.

Describe the solution you'd like
A show should be considered watched when, as an example, the last episode of the show was watched, if there's a new episode, it should be removed from watched.

Describe alternatives you've considered
I tried implementing it myself. Even implemented the filter of watched and not watched on the web Stremio/stremio-core#642 (comment), but I was informed that desktop and android source code is closed and that my changes wouldn't reflect there, therefore it would be nice to have those features there.