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.

It was causing unit tests to fail, and it's a needless bit of abstraction that
never should have existed in the first place.

Instead, we use XModule field default values when creating an empty
XModule. Driven by this use case, we also allow for XModules to be
created in memory without being persisted to the database at all. This
necessitates a change to the Modulestore api, replacing clone_item with
create_draft and save_xmodule.

saved as draft.

Fix bug STUD-103. The url base for about page links needs to be www.edx.org for Drupal site, vs. LMS_BASE which is used for Studio. Note that the complete URL is still not correct, but a redirect exists to take it to the new location.

https://edx.lighthouseapp.com/projects/102637/tickets/331

kludged in the note tab panel so it can be turned on and off using the policy editor by adding "notes" to "advanced_modules."

get _cache_children to queyr both non-draft and draft versions of the children, then overwrite all non-drafts with the draft version, if available. This conforms with the semantics of the DraftMongoModuleStore

remove unused import commands (which were used for temporary profiling). Also change get_lms_link_for_item() to preserve the previous argument ordering. Apparently all callers may not use argument name conventions for the 'preview' argument.

restore metadata inheritance. Fix lms jump computation on the Studio index page. This gets expensive.

add service entry point to generate tar.gz file and return to caller. Use of the NamedTemporaryFile will auto cleanup.