CMS import backwards compatibility
- edx4edx and 8.01x course repo errors fixed and verified
- moving forward, it would be nice if the LMS+CMS xml import failed more gracefully when encountering errors in the xml files, when in debug or authoring mode. For example, an inadvertent xml error in one problem (eg created by a mistake in an import tool used in the CMS) should not bring down the whole LMS. Ditto if one problem gets deleted from the mongodb or filesystem.
