This page is called by a XmlHttpRequest object. It requires parameters "page" and "macro":
they are used to call the macro that will render the HTML chunk to be returned to the browser.
It also requires parameters "objectUid", which is the UID of the related object. The object will
be available to the macro as "contextObj".
It can also have a parameter "action", that refers to a method that will be triggered on
contextObj before returning the result of the macro to the browser.