Added warning so that clearinghouse operators link to correct demokit.
Merge https://github.com/choksi81/clearinghouse-1

Conflicts:
	website/html/templates/control/profile.html
More work towards fixing SeattleTestbed/clearinghouse#139

Based on @choksi81's previous work, I'm making the TESTBED_URL,
mailing lists, and clearinghouse URL configurable in
website/settings.py too. I also cleaned up lots of references to
washington.edu en passant.
Merge branch 'master' into make-github-aware-#134