[cms] Language switcher breaks on language specific cms-generated slugs

[bjrne]

When creating a new page in django cms or adding a new language version of an existing page, django-cms pre-fills the non-optional slug field with a sanitized version of the localized page title.

Example:
When adding a german version of the "about" page, one sets the title to "Über uns", and the slug automatically turns into uber-uns. This is also the new url, which obviously breaks our language switcher.

A good solution is not obvious, this could be a major pain-point for non-technical users.

[Baschdl]

Maybe this would be a reason to use django-cms language switcher? See #84