'Spotify' is now imported into the root module
Added Playlist 'fetch' method to  navigate playlist folders
Created new Playlist 'fetch' method to return full item metadata (renamed old method to 'list')
Playlist 'uri' property is now filled with the original request uri
Playlist 'fetch' now returns tracks (unless it's the rootlist)
'Uri' objects are now returned from Playlist.uri
Track 'albums' changed to 'album' (only one item is returned from protobuf)