Univention Corporate Server 4.2 erratum 285 (bugfix)

This update addresses the following issue(s):
* Customize LDAP_HOSTDN env variable name.
* Upgrading an App failed when required App Settings were used. This has
  been fixed.
* Show the translated text for the license type of the App.
* Improved caching lookups to reduce startup time of the module.
* Show a rating's description when hovering over it.
* Filter UCS components is now more robust with respect to diverted caches.