Univention Corporate Server 4.1 erratum 68 (bugfix)

This update addresses the following issues:
* The syntax check for the Base64GzipText attribute type had an error
  that made it impossible to store data in such an attribute.
* The "simple" syntax class now allows None values to be able to e.g. remove
  the birthday of a user.
* Some shell quoting errors were fixed.
* Translation format strings with multiple unnamed arguments have been
  adjusted.
* It is now possible to ship translations for UDM hooks and UDM syntax
  settings.