Support streaming music/playlists

I'm a big fan of streaming music like soma.fm. I usually play a playlist like the following using Audacious:
https://github.com/tlhunter/streaming-music/blob/master/SomaFM.pls

Of course, the Music player integrates pretty well with ElementaryOS overall and I'd love to stream music via Music.

Start by examining the Music player's existing playlist and playback handling, then inspect the SomaFM.pls example linked in the issue. Determine what support for streaming playlists would need to cover and how completion could be verified in Music on elementaryOS.

Written by the indexing model from the issue text.