EDIT

  $form['drupal_integration'] = array(

    '#type' => 'fieldset',

    '#attributes' => array('class'=>array('clearfix')),

    '#title' => t('Drupal integration'),

    '#collapsible' => FALSE,

    '#collapsed' => FALSE,

    '#tree' => FALSE

  );

  $form['drupal_integration'][CDM_DRUPAL_NODE_CREATION] = array(

    '#type' => 'checkbox',

    '#title' => 'Create drupal nodes',

    '#default_value' => variable_get(CDM_DRUPAL_NODE_CREATION, FALSE),

    '#description' => 'The content of the pages created by the cdm_dataportal module is directly retrieved from the 

    CDM webservice configured above. In order to use other drupal modules like the "Comments" module together with the 

    cdm pages it is required that drupal nodes are created and stored in the database.'

  );

  $form['drupal_integration']['drop_all_cdm_nodes_warning_pre'] = array(

    '#markup' => '<h6 style="color:red;">WARNING:</h6>

    <div class="description">Using this button, you will lose all content associated with the cdm drupal nodes which is stored in the drupal data base.</div>',

  );

  $form['drupal_integration']['drop_all_cdm_nodes'] = array(

    '#type' => 'submit',

    '#value' => t('Drop all cdm nodes'),

    '#submit' => array('drop_all_cdm_nodes_submit')

  );

  $form['drupal_integration']['drop_all_cdm_nodes_warning_post'] = array(

    '#markup' => '<div class="description">All Drupal nodes created for cdm content can be deleted at once using this button.</div>',

  );

    // ----------------------

/**

 * Submit callback; drops all cdm nodes.

 *

 * @ingroup forms

 */

function drop_all_cdm_nodes_submit($form, &$form_state) {

  cdm_delete_all_cdm_nodes();

  drupal_set_message(t('All cdm nodes dropped.'));

}