VID-2142 Create a way to clear the VideosModule Video Cache

* Refactored the VideosModule into different subclasses for each video sources
* Added cache purging code
* Incorporated James' AsyncCache changes

Note: [Original PR](https://github.com/Wikia/app/pull/5750) was not based on uconn-3, and merging it was not possible. Possibly [this merge](https://github.com/Wikia/app/commit/61b09f88617638cb005c2a4c7242fca0e8788647) into the branch caused base to diverge.