* Video Player now acting as a parent that always knowing the state of
  their children.
* Events on the sub-controls are now triggered on itself, and binded by
  the Video Player instead of triggering everything on the Video Player.
* A new helper class, SubView, has been introduced to cleanup repeat
  logic on scoped jQuery selector, render() and bind()

This allows XModuleDescriptors to export themselves to XML

These changes make the LMS read from the XML course files using the ModuleStore interface. 

Note that stable-edx4edx will now no longer be a clean merge.  But this code has priority.

Acknowledge the fact that right now keystore is really just a module store. If we need a keystore that returns other objects, we can reexctract the base class into it's own module again