Deleting programs

Adds the concept of a default program, and a management command to make this happen in existing data.

Adds the ability to delete a program.

http://manage.dimagi.com/default.asp?134960
Hah, good catch, I just fixed it.

I definitely just copied this from the archive user stuff that I modeled a lot of the product work off of: https://github.com/dimagi/commcare-hq/blob/archive-programs/corehq/apps/users/views/mobile/users.py#L572-578