Univention Corporate Server 4.1 erratum 171 (bugfix)

This update addresses the following issues:
* Localization of the GRUB boot menu has been disabled. The title string gets
  translated to the preferred language of the user triggering menu generation
  process. This breaks selecting a boot kernel through the UCR variable
  'grub/default', as it doesn't work on systems using a different language.
* Remove extra argument to `grub-mkdevicemap` as it is not needed.
* Quote menu title to allow strings containing blanks.
* Disable saving the selection by default as it is not supported on all file
  systems.
* Add support to configure serial console support through the UCR variables
  'grub/terminal' and 'grub/serialcommand'. Thanks to Lutz Willek for the
  patch.