Authors can upload an image (or choose an existing one) from the
settings page, using the in-context uploader from PDF
textbooks. Includes tests for backwards compatibility with XML courses
-- they used a magic filename (images/course_image.jpg) which is
mapped to a location in the Mongo contentstore.
Still needs some UX work, though the backend plumbing is there.
A few notes:
1. Downloads are done through direct requests. This is due to the difficulty of downloading a file to the correct place
2. Modifiying a file will just change the file to a random 10 character string.
3. The page is reloaded in between uploads. This is due to a current caching bug that is in the process of being looked into and will be updated once it is fixed.
