allow for optional 'COURSE_DIR' parameter for the import rake target so that we can import only a single course

fix up some thumbnail issues. Also we need to manage the user permissions when we clone and delete course

initial commit. Add 'import_path' field to the GridFS so that when we export, we know where it originated from

Provide more info when django has issues when running from rake, and don't install dependencies of common/lib/libraries before every run of a django command

Modify rake file to read in spec and src files correctly and also add in the lms helper file for stubRequests, etc.

initial xlint implementation. Accumulate all import errors during XmlModuleStore importing. Also do checks post XmlModuleStore import and assert that the structure (course->chapter->sequential->vertical) is present in the courses.

Put the coverage data files in the reports dir, where they will be treated like the disposable things they are.

Split out requirements that come from the local mitx repo and those that come from github, and upgrade the local requirements before running tests

Only allow django-admin to run in reload mode when browsing jasmine tests, and only kill the whole process group in that case (so as to know kill jenkins)

- Add tasks to test lib without coverage
- Add a coverage flag to test.py (set to True, for manual tweaking for now)