Modify export_to_xml to take an optional contentstore and work with xml courses
Add command to dump the course_ids available to the LMS
Add command to dump the structure of a course as a JSON
Add command to dump a course to stdout as a tar.gz file
Delete dump_course_structure django command on cms

Replaced by dump_course_structure on lms
Merge pull request #1289 from rocha/dump-course-command

Export course command