edX Course/Library Import/Export API

This is a public, versioned, RESTful API for importing and
exporting full course content. The code was initially ripped from the
existing import/export API in the CMS contentstore djangoapp and wrapped
in Django Rest Framework view classes. It's a new djangoapp in
the openedx directory which is largely an abstraction off the CMS
Import/Export views.

This PR includes configuration changes. Most notably, Studio is
configured to serve the OAuth2 provider alongside the LMS.

This is the initial thread on the code list:
https://groups.google.com/forum/#!msg/edx-code/DmnHWmly25A/ZqjD1zb4o7oJ

And this thread contains another description of the changes:
https://groups.google.com/d/msg/edx-code/6dP9SEKsmqQ/Pvyn8fBDx68J

There are a numerous non-covered lines, all of which are missing
coverage in the CMS API this was ported from. They're mostly error
conditions, such as handling of multipart file upload errors.