l10n: de.po: prepare "de.po" for new translations

This is just a preparation commit which applies
"msgmerge" to "de.po".

Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com>
l10n: de.po: translate 35 new messages

Translate 35 new messages came from git.pot update
in 9caaf23 (l10n: Update git.pot (35 new, 14 removed
messages)).

Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com>
Acked-by: Thomas Rast <trast@inf.ethz.ch>