Added German translation, corrected a few English phrases

Signed-off-by: Jan-Christoph Ihrens <ihrens@cc-services.de>
Merge pull request #31 from enigmatic-user/german_translation

German translation
Updated UI with buttons instead of just right click menu
Merge remote-tracking branch 'origin/develop' into develop
formz-30 Export Submissions #30
Version 1.0.0-rc2 ready