Branding for GeneNetwork

GN Guile provides a branding mechanism for GN.

To redirect a URL in nginx do something like:

    server_name aging.genenetwork.org;

    location / {
        proxy_pass         http://127.0.0.1:8091/;
        proxy_redirect     off;
        proxy_buffering    off;
        rewrite ^/$ /home/aging last;
    }

it redirects the base URL to the page rendered in web/view/brand/aging.scm