Univention Corporate Server 4.2 erratum 79 (bugfix)

This update addresses the following issue(s):
* It is prevented to move or remove the own object now.
* It is now checked if the create, modify and remove operation is allowed
  before executing the action.
* Objects of type Settings: Service were not editable through the
  LDAP directory module. This has been fixed.
* An error during creation of existing objects has been fixed when policies
  should be referenced.
* The descriptions of properties belonging to print quota policies have
  been enhanced.
* The "Span both columns" option for extended attributes is functioning
  again.
* An error is prevented when trying to attach an unknown object class to an
  object.
* It is now possible to hide existing properties in the layout via an
  extended attribute.
* More descriptions have been added to the windows settings of user objects.
* The UDM CLI now shows a readable error message when the LDAP server is not
  available.
* The home share and home share path properties are now correctly displayed.
* It is now possible to remove values from Univention Config Registry
  policies via CLI.
* The udm --help output has been cleaned up to improve readability.
* The --position argument has been added to the --help output of the udm
  list command.
* The layout of container objects has been adapted so that the configuration
  options for default containers are visible on the "General" tab.
* The license evaluation now respects renamed default user and group names.
* Searching for the printmodel property in printer driver lists is working
  again.
* The DN of objects removed with udm remove --filter is now displayed.
* Legacy and unused code has been removed.
* The ObjectFlag syntax now allows the value "synced".
* The syntax check for udm search filter has been improved.
* The performance of search filters for user objects has been improved.
* The output from the list command of the UDM CLI is now sorted.
* Legacy code related to custom attributes has been removed.
* The listener module for handling UDM extensions now removes old python
  files when the file was renamed.
* A programmatic error when creating container objects has been fixed.
* Error messages now contain more details in case of errors with invalid
  LDAP DN syntax.
* The remove operation of the UDM CLI now allows the option
  --ignore_not_exists.
* A package dependency to python-ipaddr has been added.