l10n: de.po: translate 241 messages

Translate 241 messages came from git.pot update in 673bfad
(l10n: git.pot: v2.12.0 round 1 (239 new, 15 removed)) and a4d9483
(l10n: git.pot: v2.12.0 round 2 (2 new)).

Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com>
Acked-by: Phillip Sz <phillip.szelat@gmail.com>

Author: ralfth