Refactor base templates for DRY.

* Reuse same markup for mobile and desktop.
[bug 916079] Send HTTP users to /users/login which forces HTTPS.

Only applies if SESSION_COOKIE_SECURE=True
Require SSL on get involved pages.

Since they can sign you in directly via persona.
[bug 918393] decode url before passing to persona

This is a workaround for:
https://github.com/mozilla/browserid/issues/3903