[web] Move request handling logic into cubicweb application. (closes #2200684) We improve http status handling in the process: ``application.publish`` have been renamed to ``application.handle`` to better reflect it's roles. The request object gain a status_out attribute to convey the HTTP status of the response. WSGI and etwist code have been updated. Exception gain status attribute

$(document).ready(function() {
    $('a.rhythm').click(function (event){
        $('div#pageContent').toggleClass('rhythm_bg');
        $('div#page').toggleClass('rhythm_bg');
        event.preventDefault();
    });
});