Univention Corporate Server 4.2 erratum 167 (bugfix)

This update addresses the following issue(s):
* The S4 Connector now handles invalid pickle files.
* The S4 Connector synchronizes attributes with a case sensitive compare.
  Previously a case insensitive compare was the default.
* An error during removing a GPO has been corrected.
* The detection of the primary group during creation of user objects with
  special characters in their samAccountName has been fixed.
* UCS@school specific settings have been moved into the join script.