Bug 20683: Update German web installer for 18.05

Bug 20683: Update German web installer for 18.05

Adds translations for 2 new notices CANCEL_HOLD_ON_LOST and
CHECKOUT_NOTE.
Some small changes to older notices to match them with the
English templates.

To test:
- Install German
- Run the web installer on an empty database
- Make sure all files install correctly and there are no SQL
  errors
- Check notices were loaded correctly

Signed-off-by: Mirko Tietgen <mirko@abunchofthings.net>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>