[Tails-l10n] [de](review) update and complete about.de.po

ThreadAuthorDate (-000)
M\Frithjof2014-01-06 22:30
M|sajolida2014-01-07 16:35
M|Frithjof2014-01-07 20:11
|MJens Kubieziel2014-01-07 21:53
Msajolida2014-01-08 11:47