Taking Ike's delete-student-state-for-problem code and putting it in a separate PR so it's not bundled with more debated features.

- make category a data field of an input
- namespace event types
- don't try to use the track function when it doesn't exist
- generate event types if it doesn't match a pre-existing pattern

- removed duplicate logos.
- cover images are still in the 200-350 KB range.

Still waiting on transparent logos.

  - ops view for the desktop app to talk to
  - xmodule that talks to the foldit model and displays the student's state
  - grading tweak to make grade updates from an external service work:
    - Add an always_recalculate_grades property to XModuleDescriptor.

Updated all coffee scripts to define and use Alpha version of classes. Added missing functions for HTML5Video.Player prototype. Now bare bones works without errors. YouTube version also works without errors.

Adding HTML5Video class and modifying coffee sources to use it when video sources are provided instead of YouTube IDs.