Add support to play videos on chromecast.

This is actually my main interest in the project.  I don't have a vita, but I do have a chromecast, and want to be able to easily play my videos on it.  

This patch adds basic support to play the videos on the chromecast from the browser when a cast receiver is available.  Is there any interest?  I could buy you a chromecast if you don't have one :)