Clean up UI for Users

To make things more clear to the end users it would be nice to box out the notify new content and Content options so they understand those two go together.

something like this:

    $form['notify_page_detailed'] = array('#type' => 'fieldset', '#title' => t('Detailed settings'));
    $form['notify_page_detailed']['node_notice'] = array(
    '#type'         => 'fieldset',
    '#collapsible'  => true,
    '#collapsed'    => true,
    '#title'        => t('Changes to nodes'),
    );
    $form['notify_page_detailed']['node_notice']['node'] = array('#type' => 'radios',
      '#title' => t('Notify new content'),
      '#default_value' => $notify->node,
      '#options' => array(t('Disabled'), t('Enabled')),
      '#description' => t('Include new content in the notification mail.'),
    );
    $form['notify_page_detailed']['node_notice']['teasers'] = array('#type' => 'radios',
      '#title' => t('Content'),
      '#default_value' => $notify->teasers,
      '#options' => array(t('Title only'), t('Title + Teaser'), t('Title + Body')),
      '#description' => t('Select the amount of each post that you would like to see in your notification e-mails.'),
    );