Added a control dock
Added format option for song label
I haven't tested the dock for Spotify since I don't have premium, but it should technically work

Fixed music control dock not saving it's state
Fixed music sources not using placeholder when playback is paused

Also I noticed that Spotify is limiting the api requests, so if your info isn't updating sometimes
it's probably because the plugin has to wait a certain amount of time before it can send another request.