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.

fix (again) static_replace to work with static_asset_path

Letting xblocks handle scope rather than separating fields into
different attrs. Although, split still shunts content fields to a
different collection than setting and children fields.

The big difference is that content fields will always be a dict and not
sometimes just a string and there's no special casing of 'data' attr.

The other mind change is no more 'metadata' dict.

Fixed all common and LMS tests.

The tests were failing because XMLDescriptor adds in some attributes
to _model_data, such as `xml_attributes`, that aren't necessary. The
solution is to handle all XML parsing in VideoDescriptor. There's
still one test failing in CMS, which has to do with metadata being
saved. I'm still working out how to update it in such a way that it
doesn't fail, but still tests something meaningful.

add ability to rewrite links on the old /courses/<org>/<course>/<run>/jump_to/i4x://&lt;org&gt;/&lt;course> .. intracourseware linking to the new portable /jump_to_id/<id> format

change from_xml class method on video class to make sure we honor the fact that the xml string could actually be a pointer to another file on disk which actually contains the attributes

A new modulestore backed by mongo that changes the data format to
facilitate easy versioning, sharing content between courses, and fast
lookup of course structure and Scope.settings data.

Conflicts:
	cms/djangoapps/contentstore/tests/test_contentstore.py

add a default XML serialization if the 'data' field is empty or None. Some XModules now - like video XModule - do not have XML set in the 'data' field

Also fixed things in the toy course where needed

Factories were used when possible but tests depending on importing or things not manageable by factories used the toy course.  New files were added to include the needed functionality.  Most files are blank or have minimal xml needed to work

A blank asset file was also added to toy

This fixes the following tests(T stands for toy, F stands for factory made):
T import_textbook_as_content_element (needed to add a textbook to toy)
F static_tab_reordering
T import polls (needed to add a poll to toy)
T xlint_fails
F delete
T about_overrides (needed to add an about override to toy)
F remove_hide_progress_tab