Univention Corporate Server 4.2 erratum 115 (bugfix)

This update addresses the following issue(s):
* Some spelling mistakes in the UDM CLI Client have been corrected.
* Unused legacy code has been removed.
* Legacy code regarding the ordering number of extended attributes has
  been cleaned up.
* A lookup function for the users/self and users/passwd modules have been
  added for convenience.
* The error handling during adding hosts to nagios services has been
  improved.
* The temporary locking objects are removed when an error happens during
  object creation. This prevents that one needs to save an object
  twice to create it after resolving the error.
* It is currently possible to supply a wrong object type when modifying
  objects. This erratum prepares for preventing this by adding more error
  messages to the logfiles instead.
* UDM objects with the object flags synced and docker can now be deleted.
* Passing univention.uldap.access() instances to UDM objects is handled more
  gracefully.
* The detection of DNS TXT and Host records has been improved to not detect
  objects as the wrong type.
* The description for the "options" property of extended attributes
  has been improved.
* An LDAP error is prevented when changing the user password and the
  "Change password on next login" option at the same time.
* Unused legacy code regarding container/dc objects has been removed.
* Some undefined python references have been fixed.
* Removing the IP range from a network object is possible again.
* The "hosts" property has been added to the settings/umc_operationset.
* The "description" property of settings/umc_operationset is now a
  required field.
* It was not possible to automatically get the next free IP address for
  a newly created computer object when the license was exceeded.
* The group members of printer groups with multiple spool hosts are now
  detected correctly again.
* The validation when removing and modifying printers and printer groups
  has been corrected.
* The "Spool Host" label of printers and printer groups has been renamed
  into "Print server".
* The "e-mail" property of a user is no longer copyable.
* Support lookup of specific attributes via PostReadControl (RFC 4527)