XWIKI-9061: Property displayers don't work in the object editor for objects that have just been added
* Add Velocity macros for inserting the Skin Extension hooks (in order to avoid duplicating code)
* Output the skin extension hooks in editobject.vm when an object is added via AJAX so that property displayers can pull CSS/JavaScript resources.
* Move the CSS/JavaScript includes to the page head and fire xwiki:dom:loaded after an object had been added via AJAX.
* Add support for xwiki:dom:updated event in date picker.