Responsive stylesheets

There are some key changes in `files/templates/header.htm` to be aware of, including addition of id `nodeinfo` to differentiate that table from other tables using `status-bar` class.  Styling is problematic otherwise.  Mobile stylesheet is linked first, with stylesheet for larger resolutions linked using media queries below that.  This is intentional, because mobile devices that don't recognize CSS3 media queries should ignore the larger format.  (With cascade effects for accessibility devices, text-mode browsers, and really old browsers).

To test, use a mobile device (and also generate an error post-quickstart).

cc @elationfoundation @critzo