public function addSetting($name, $label, $renderer = null, $args = null, $default = null)
    {
        if (!$renderer)
            $renderer = array($this, 'createSettingsTextbox');
        $this->settings[] = array('name' => $name, 'label' => $label, 'renderer' => $renderer,
            'args' => $args, 'default' => $default);
    }