Don't function call on null

Feature/victor/per course status

* makes testing easier -- don't need course objects

Victor/capa cleanup

Looks good.  Yes, the code exec part will need more thought, particularly with respect to security.

Don't want to break existing problems.

This reverts commit 811422a1.

- check for known script type instead of ignoring js and perl

Now looks for a status_message.json file, looks for 'global' and ${course.id} keys. Return any global message and any course-specific message, joined by <br>.

fab files need to be updated to use this new format (new filename, possibly also help manage per-course messages, or at least test for valid json)

Added starting_index conf to AssignmentFormatGrader.

Added starting_index conf to AssignmentFormatGrader. Added a bit of forwards compatibility for new grading policies.

added ie warning banner to courseware; displayed by ie conditional style...

Set git push.default to current on the create-dev-env script

Fix error when creating empty associations

move output right/wrong image to top left of each test instead of center

Also renamed some variables to make them more distinguishable

Use django cache for OpenID provider store

changed vote button icon display mode to fight zoom bugs

added google analytics to all pages without a course object

Fix create-dev-env script for Mac OS 10.8 and latest stable rvm

Add support for video download link

Replaced the previous method of getting it from HTTP_POST to use
django's mechanism, which may or may not use HTTP_HOST. However if an
attacker changes the request header, there is not much he can do since
he cannot recreate the association nonce.

Now when you hit the TAB key in codemirror, it will insert 4 spaces.