Allow authentication via a JWT in a cookie

[mrclay]

If the system detects there's no Basic auth protection, it falls back to a traditional login form with session in JWT cookie. Like Basic auth, an admin still has to create the user's directory (I think this is wise), but once created the system will let you register.

My end goal here is to be able to deploy this on my host (without any custom Apache config) with URL paths like /subdir/b.php?u=username.