Django 1.4 upgrade

This seems to work, might as well have a PR open.

You'll also need my fork of kuma-lib, and you'll need a virtualenv that has Django 1.4.5 installed and on your path somewhere ahead of our stock Django. Which means jenkins is going to throw up all over this, and you'll need to test locally.

Unit tests for apps we actually use should all pass, except for some in sumo that have been broken forever (due to relying on forums), and some in the wiki that want Site and Permission objects to be created during the test run.