Multi-site support.

Related to #2.

This is a pretty basic initial implementation of also supporting GameSpot/ComicVine. Needs a decent amount of additional work. At minimum:

* Remove checking for GameSpot/ComicVine going live and related settings. That is apparently not going to be supported in the JSON data. On the flip side, if it does end up being supported, would need to handle multiple simultaneous streams.
* Display which site each schedule item is from.
* Sort schedule items based on date. Right now each site's schedule items are grouped together.
* Filter option to just see one site's schedule at a time.