l10n: de.po: translate 9 new messages

Translate 9 new messages came from git.pot update in a4156d2
(l10n: git.pot: v2.5.0 round 2 (9 new, 5 removed)).

Signed-off-by: Ralf Thielow <[email protected]>
Acked-by: Phillip Sz <[email protected]>

Author: ralfth