Allow user to delete account

[buren]

We must add a way to allow users to delete their account. To begin with we can add it at the very bottom of the show profile page (in red or some other warning colour) and also have a "are you sure?" confirmation dialog.

If the user proceeds with the deletion we must also display a message stating that they still have an active Frilans Finans account and if they wish to delete that too they must contact their customer service.

Replaces justarrived/just_match_api#445