Bug 11828: (follow-up) add new option to OrderPdfFormat

Bug 11828: (follow-up) add new option to OrderPdfFormat

To test:
- Check appearance of the OrderPdfFormat system preference
  It will offer a pull down with options, including
  "German 2-page"

Followed test plan. Patch behaves as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>

(cherry picked from commit 6372689f5dc7f0e9d34ffef3ad0c2a1ab6d6fb58)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>