Valera/video alpha2 refactor

This is the Video Alpha version 2. A refactored version of the Video Alpha which is currently in master. Several key differences:

1.) Controls are auto hidden after a delay of mouse inactivity - the full video becomes visible.
2.) When captions (CC) button is pressed, captions stick (not auto hidden after a delay of mouse inactivity). The video player size does not change - the video is down-sized and placed in the middle of the black area.
3.) All source code of Video Alpha 2 is written in JavaScript. It is not a basic conversion from CoffeeScript. The structure of the player has been changed.

It is fully backward compatible with the original Video Alpha XModule, and with the Video XModule. It is a drop-in replacement.

The Jasmine JavaScript tests have been rewritten and updated. There are 9 test files. All of them pass individually. However, if all of them are turned on, then on some systems the browser hangs. Please see the file
common/lib/xmodule/xmodule/js/spec/videoalpha/readme.md

@rocha and @peter-fogg please review!