Sets the button for this wizard for the inputed type.

        :param      which  | <XOverlayWizard.WizardButton>
                    button | <QtGui.QPushButton>

def setButton(self, which, button):
        """
        Sets the button for this wizard for the inputed type.

        :param      which  | <XOverlayWizard.WizardButton>
                    button | <QtGui.QPushButton>
        """
        try:
            self._buttons[which].deleteLater()
        except KeyError:
            pass

        button.setParent(self)
        self._buttons[which] = button