[Feature Request] Ability to listen to already cached/listened songs for offline listening

I love seeing what part of the song was already buffered. I would suggest a setting to set a cache limit and cache already listened songs. Those would also be available when offline. I listened to a song, waited till is was fully cached and turned offline mode. The song wasn't available, obviously. that feature could save some headache on frequently listened songs without the end user having to manually download them.

I would make the cache quite dumb, when the limit is reached just delete the oldest played cached song.

Also add "big" numbers 1GB, 2GB, 5GB... and unlimited. I believe Audinaut have a similar setting if a contributor or the author wants to take a look.