Port SettingsVarsDebugPanel from Django DebugToolbar

This code works on my Ubuntu 13.04 x64 box under Python 2.7.

Please let me know if you need anything from me in addition.

This code will not work on Python < 2.7 due to collections.OrderedDict usage without any fallback:
http://docs.python.org/2/library/collections.html#collections.OrderedDict