Support additional room modes

[dasevilla]

• Shared: Everyone can add and vote on tracks (current option)
• Broadcast: Only one DJ, everyone else listens
• Round-robin: Each DJ has their own play queue (turntable.fm style)

[superemily]

• Private parties

[iangilman]

• Albums instead of tracks

[MikeNGarrett]

• Battle Royale: current DJ plays until getting voted off the stage