Spotify search should support filename/uri

[adamcik]

As far as I can see the spotify search does not support uri lookups, i.e. we probably just want to lookup the track and return it.

[jodal]

Spotify search by track URI now works. Probably you'll see a "[loading...]" track in the search result, but by the time you add it to the tracklist it will have metadata.

SpotifyTrack <3