Add a default login frame template that you can include into your apps

This frame handles things like preserving the URL when you redirect and
redirects into an unboxing page. Requires Javascript, but that's how
the cookie crumbles.

Remove the now unrequired code paths.

To use in an app:

LOGIN_URL = 'home'  # a page that includes login-frame.html
LOGIN_REDIRECT_URL = '/unbox'
Set 'next' to either the outer frame next or LOGIN_REDIRECT_URL

Move unbox to ixlogin so that it's out of the way of the main namespace.