Static file serving in the url dict

We dont yet have a nice way of serving a directory of static files from the URL map (or indeed a single file). Something like the following should be made possible:

app.urls = {
    '/scripts: { static: DOC_ROOT+'/static/scripts' }
}

and have it serve files (no dir index) with the correct doc type, and ideally the right cache headers – ETag, Last-Modified at the least