Navigation bar cleanup

* Reordered/removed "hardcoded" navigation bar elements such as the language switcher and the help menu. (In anticipation of https://github.com/my-koop/service.website/issues/185)
* The top-left logo now redirects to the homepage.
* The language switcher now works properly.
* Exposed meta information for French and English languages.

Addresses the first half of https://github.com/my-koop/service.website/issues/234.