Write basic description of APIs

[hyperblast]

Swagger does not seem convenient to explain this. We need more info on how parameters are encoded (especially array ones), structured errors, etc.

[Barabba11]

Hi, I've the same problem, for example I want to load a playlist, how can I point the file? I've placed the file in the music folder declared in options, nu I can't open it: http://127.0.0.1:8880/api/playlists/add/radio_alternative.m3u

I'm also looking for how can I change foobar volume with api. Thank you a lot for supporting!