Add CronCommand - a command that can only be run from the command-line.  Why you'd want this: to interact with chronograph easily, but to force the command to be run within the server process.
Merge branch 'develop' of github.com:learningequality/ka-lite into 1477

Conflicts:
	kalite/updates/management/commands/videodownload.py
remove auto-pdb from automatically added args when DEBUG = True
Merge pull request #1648 from bcipolli/1477

Add CronCommand - a command that can only be run from the command-line.