Allow multiple sources for JW player

JWPlayer allows [multiple source](http://support.jwplayer.com/customer/portal/articles/1428524-hd-quality-toggling) files for different bitrate for users to choose from a menu

![Alt text](https://monosnap.com/image/8zeWQiT4Iw2Uw5DOGeMvhT5LxWwpQn.png)

This PR attempts to give them flexibility to popcorn while not breaking existing usage. If accepted, I will be happy to update the docs as well.