code: protected Fragment newModalFragment(final String id, final String markupId,
  		final MarkupContainer markupProvider, final IModel<T> model)
  	{
  		final Fragment fragment = ComponentFactory.newFragment(id, markupId, markupProvider, model);
  		return fragment;
  	}
docs: Factory method for creating a new {@link Fragment} for the content of the modal dialog. This
  method is invoked in the constructor from the derived classes and can be overridden so users
  can provide their own version of a new {@link Fragment} for the content of the modal dialog.
  
  @param id
  the id
  @param markupId
  The associated id of the associated markup fragment
  @param markupProvider
  The component whose markup contains the fragment's markup
  @param model
  The model for this fragment
  @return the new {@link Fragment} for the content of the modal dialog.