Univention Corporate Server 4.1 erratum 88 (bugfix)

This update addresses the following issues:
* The SAML logout process is now more robust.
* Missing translation files won't cause a HTTP 404 Not Found error anymore.
* Translation format strings with multiple unnamed arguments have been
  adjusted.
* Internet Explorer 11 doesn't show a download pop up anymore when accessing
  UMC.
* The versions of outdated browsers have been updated.
* Some minor usability adjustments for the login dialog have been
  implemented.