Univention Corporate Server 4.4 erratum 547 (bugfix)

This update addresses the following issues:
* Added UCR variables to enable admins to switch off all pages (and backend
  functions) individually.
* Users can now request the deletion of their account on the "Your profile"
  page of the Self Service. This feature can be activated via the
  umc/self-service/account-deregistration/enabled UCR variable.
* When requesting a new token, do not disclose the email address of the
  user.