Some editing

Some editing
Fix permissions
Add help text to describe import format
Complete German translation
Fix typo: seperate -> separate
More German translations

Since plonesurvey-plone.po contains translations for the same messages as
plonesurvey.po, I just used:

i18ndude admix plonesurvey-plone.po plonesurvey.po >plonesurvey-plone.po2
mv plonesurvey-plone.po2 plonesurvey-plone.po