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
it likely doesn't matter all that much, but you could get away with calling the view manually (or adding params to the function) so that it doesn't use `include_docs=True`. This would be significantly more efficient.