Allow users to delete their profile

[jasonaowen]

Allow a user to delete their profile, and all their projects (see also #48, which needs to be done first).

I don't know how exactly this should work. We fetch, store, and use some data about Recursers from the RC API, and I don't think deleting a user profile would alter any of that data. Is it better to delete the User record and leave behind some kind of deleted user record? Or is it better to hold on to some of the User record, clear the user-entered data, and mark it as inactive? If someone who deleted their profile logs back in again, what should happen?