Pass multiple songs

[abauer]

so that player can cache songs for the future

[ThomasGaubert]

Presumably this will result in an API change. Something along these lines (tweaked to provide data as needed) would work:

{
  "id": "3C835F185DB2B",
  "timestamp": "1422905167",
  "state": "PLAY",
  "nowPlaying": {
    "service": "GOOGLE_PLAY_MUSIC",
    "user": "tgaubert",
    "stream_url": "http://...",
    "metadata": {
      "title": "Dangerous (feat. Joywave)",
      "artist": "Big Data",
      "album_art": "http://...",
      "artist_art": "http://...",
      "song_id": "Jyr2eDr1v1"
    }
  },
  "queue": [
    {
      "user": "tgaubert",
      "stream_url": "http://...",
      "metadata": {
        "title": "Ghosts 'n' Stuff",
        "artist": "deadmau5",
        "album_art": "http://...",
        "artist_art": "http://...",
        "song_id": "v93F5yEz2X"
      }
    },
    {
      "service": "YOUTUBE",
      "user": "other user",
      "stream_url": "http://...",
      "metadata": {
        "title": "Jungle",
        "artist": "X Ambassadors, Jamie N Commons"
      }
    }
  ]
}

cc @grantaclaus

[abauer]

@grantaclaus had an idea for this; not sure his exact plans but "I know how to do this"