The XML attributes used in AbstractWidget.generateSaxFragment(ContentHandler, Locale)
to be placed on the wrapping element for all the XML-instance-content of this Widget.
This automatically adds @id=AbstractWidget.getRequestParameterName() to that element.
Concrete subclasses should call super.getXMLElementAttributes and possibly
add additional attributes.
Note: the @id is not added for those widgets who's getId() returns null
(e.g. top-level container widgets like 'form'). The contract of returning a non-null
AttributesImpl is however maintained.
Handle the fact that this action was activated. The default here is to perform any
action associated to this object, end the current form processing and redisplay the
form.