Open in music fileaction

@kabum please review an inital version of a files action. I added a route to the js part and another one to the api. see commit messages for details. I'm especially unsure about the $routeChangeSuccess and SoundManagerReady hooks:
* SoundManagerReady should start the playback when the page is first loaded
* $routeChangeSuccess should trigger the playback when the user manually changes the url

ultimately the url should change and reflect the currently played song. Maybe with an #/artist/345/album/345/track/345 or just #/track/234 schema.

opinions? @bantu @DeepDiver1975