Bug 10050: Update German web installer files for 3.12 - Language settings

Bug 10050: Update German web installer files for 3.12 - Language settings

Activate German and English for OPAC and intranet by default.

To test:
- Run the German web installer
- Check that when logging into Koha the German interface is shown
  and you can switch between English and German using the links
  at the bottom of the page
- Check language relevant settings in the system preferences
  are correctly set

Note: The German po files in master are buggy, please
use files from translate.koha-community.org for testing.

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>