Add a language toggle

[Seraphiana]

Objective8 should have a language toggle so that users can change the language to differ from the language that their browser runs in.

This toggle should be visible on all pages, and should use a cookie to set the language if the user is not logged in, or should add a variable to the user's profile if they are logged in.

These variables should be preferentially used by the translations that are already implemented, before defaulting back to the browser's language if they are not set