Get Playback State enhance

[sekkure]

Right now playback state will return you information about devices, current track that might be active or paused.

But here is little problem with that.

If you close Spotify and then launch it again without playing any track and try to get information of playback state it will return empty response, but why if you have active device and didn't start listen to something yet?

Would be really nice if this request will return device that is active and other fields for example track: null. So we can guess by this information that user has active device and didn't start listen yet. 

For my app it would save one extra request to API. Because right now I need to check for active device, and then for playback state because of that behavior of playback state request. Would be really cool to get all needed information in a one go.