Spelling mistakes and some additional german translation

leaving out the excessive use of html tags in the descriptions.

via: https://twitter.com/farbenstau/status/616544402887057409

While there, zap unused code and let the other languages be picked up
by xgettext as they don't print anywhere like that.

Individual commits squashed:
  Create de-de.po
  Update de-de.po
  spelling
  missed plural form

Hooked up de_DE.po correctly while at it.  Thanks!  :)

Unsetting LAN, later setting it will strip the defaults from the
interface section so try to avoid that by always settings defaults.