Add sysadmin dashboard - for seeting overview of system status, for
deleting and loading courses, for seeing log of git imports of courseware.
Includes script for importing course XML from github site.

(cherry picked from commit e949c273d01bbdfc7b5540d082e35b45838e0611)

Conflicts:
	lms/envs/dev.py
add mongoengine to requirements

(cherry picked from commit 29929c62a5d407eb7df530c60fa051c8488f5b5d)
add mongoengine to requirements

(cherry picked from commit 29929c62a5d407eb7df530c60fa051c8488f5b5d)
This is a major revamp to make the sysadmin dashboard testable and
more portable to different installation types and situations.

(cherry picked from commit 9b8b89a9cc6cc33aed84b4de73b7745d0c0f5b0a)

Conflicts:
	lms/envs/dev.py