Make user deletion a self service

[noqqe]

User deletion should work as a self service. Currently some SQL statements are sent to the site admin address.

if user clicks delete on settings page he/she should start the following workflow:

• mail with confirmation link goes to user
• user clicks confirmation link and gets to a confirmation page
• user must enter his password and tick a checkbox to confirm the deletion
• deletion is performed (if above workflow is done)