Fix the HTTP_HOST value.

Some servers adds the SERVER_PORT to the HTTP_HOST index. I'm not sure if this is the correct behavior… Buggy?
Automagically sets the correct content-type if not set.

If the Content-Type header is not set, the Controller will try to set it up for you.
Requests made using XMLHTTPRequest will add the 'application/json' to the Response.
By the way, if the request was made with HTTP_X_PJAX header set to 'true', the Controller will add the text/html content type :) text/html in any other case.

Also, I've added the 'auth' and 'user' variables into the view.
clean up! References to  and use inheritance