Allow user to request account deletion / reject already accepted disclaimer

So far user can not delete their own account. For the  moment wir do not want to make this possible by the user himself, however we need to show the user how to reject an already accepted disclaimer (by requesting the deletion of the user account). This is required by DSGVO. 

A simple solution is to add a button below the disclaimer in the user settings that triggers a mail form with a prefilled subject/body template text in modal dialog window.