[ajax] refactor/cleanup low-level ajax functions
* loadxhtml/replacePageChunck/reload_component/reload_box deprecated in favor of loadXHTML / ajaxFuncArgs
* some other cleanups in cubicweb.ajax.js
* add js_render which will replace js_component (more generic, nicer argument passing handling)
$(document).ready(function() {
$('a.rhythm').click(function (event){
$('div#pageContent').toggleClass('rhythm_bg');
$('div#page').toggleClass('rhythm_bg');
event.preventDefault();
});
});