l10n: de.po: Fix typo: Schießen -> Schließen.

That's a funny one since "schießen" means to shoot :)

Signed-off-by: Andre Noll <maan@systemlinux.org>
l10n: de.po: Update German translation

Signed-off-by: Andre Noll <maan@systemlinux.org>
l10n: de.po: Change translator email address.

Although the old address is still working, the new one should
be preferred. So this commit changes all three places in de.po
accordingly.

Signed-off-by: Andre Noll <maan@tuebingen.mpg.de>