fix for #536
Hotfix: /wiki/preview is required for all previews...
Merge pull request #540 from NicoleRauch/hotfix

Hotfix: /wiki/preview is required for all previews...
Oops, typo...
How on earth could this ever have worked?!
i18n'ed validation error page.
i18n'ed 404 and 500 error pages.
fix for #536
fix part 2
Merge commit '56e392ad20bbe113ed05558b4916ef4068a4fbf5'