Univention Corporate Server 4.0 erratum 243 (bugfix)

This update addresses the following issues:
* Proxy settings were accidentally removed when changing network settings.
* The network mask is not overwritten in the initial UCS configuration
  anymore if if was set manually.
* A typo in the German translation has been corrected.
* If accessible, the name server specified via DHCP is pre-configured on the
  network settings page.
* The links on the last page of the setup wizard have been adjusted.
* A non authoritative DNS answer is now correctly handled during validation
  of settings.
* A information is shown during domain setup that the process might take a
  while.