l10n: de.po: translate 48 new messages

Translate 48 new messages came from git.pot update in
9eb3984 (l10n: git.pot: v2.8.0 round 1 (48 new, 16 removed)).

Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com>
Acked-by: Matthias Rüster <matthias.ruester@gmail.com>