Account deactivation

Implemented user-facing account deactivation functionality
Whoa! this method! Please don't use it. I want to delete it. It's maybe the worst method in Loomio right now. Please just use a standard confirm: arg on the form or button. Check out app/views/groups/memberships/coordinator_index.html.haml for an example of a standard confirm. P.s. Don't feel bad for doing this :)