moving messages to 'status' AJAX call (no point to make its own API call, yet); adding client-side JS interface for display
moved generic scripting out to khan-lite.js, use cgi.escape to be safe with message content
Merge remote-tracking branch 'upstream/develop' into ajax_messaging

Conflicts:
	kalite/main/views.py
Only escape strings not explicitly marked as safe.
more code massaging for disk space efficiency, comments, and nit-fix
Merge pull request #126 from bcipolli/ajax_messaging

Ajax-based messaging on the distributed server.