ExtEventAjaxBehavior should not log warning when getParameters is not overridden

The method ExtEventAjaxBehavior#getParameters always logs the warning "No parameters were specified for this ExtEventAjaxBehavior. Return an empty array if there really are no arguments to the callback function.". This 'forces' custom behaviors to override this method, but that's only noticeable at runtime.

A better solution is to add a constructor that requires parameters, and mark the current default constructor as deprecated.