update ajax tools

We have to set the autoRender to true again, because CakePHP set it to false (see: https://github.com/cakephp/cakephp/blob/2.4.0/lib/Cake/Controller/Controller.php#L757). Otherwise the render method of the AjaxComponent will never be triggered on a redirect and the redirect variable is 
useless.

Another possibility would be to remove the _redirect viewVar and check with javascript only for 200 response code but you get always the 200 response code and then you don't have an identifier if a redirect happened.

For error prevention we also have to change the conditions of the render method.

If you have some imporovements, let me know :)