- until now, that first_language column in the volunteers view wasn't
  fullfilling the specs. It was simply the first language_skill the volunteer
  had added. That could have been any language. First language would have
  been a matter of luck.
- if there is more than one native_spoken language, german is taken as first
  language, if it is in the list, or otherwise it will just be the first pick
  of native spoken languages
- other languages exclude the one that is considered first language