Allow users to hide the skip button via hook_msnf_info_steps_alter()

We needed to let users to "go back" to the final step of the multi-step form from a node checkout workflow [ i.e. node/add/type multi-step > checkout <> node/NID/edit] as one continuous step form, and during the node/add part we hide the skip, but on the edit part, we needed to be able to go to any step.

So I used the alter to update the available buttons if it was an edit (note: only possible with the patch from #1967284: Calling drupal_alter() with too many parameters) and this required this patch.

This only targets skip, but could be extended out to the other buttons.

i.e. Example usage:

/**
 * Implements hook_msnf_info_steps_alter().
 */
function HOOK_msnf_info_steps_alter(&$steps_cached, $entity_type, $bundle) {
  // Provides a fallback if http://drupal.org/node/1967284 is reverted.
  if (is_array($entity_type)) {
    extract($entity_type, EXTR_SKIP);
    $bundle = $entity_type['bundle'];
    $entity_type = $entity_type['entity_type'];
  }
  if ($entity_type == 'node' && $bundle == 'goto') {
    if (user_access('administer gotos')) {
      $steps_cached[$entity_type][$bundle] = array();
    }
    elseif (!empty($form['node'])) {
      $node = $form['node'];
      if (!empty($node->nid)) {
        // Let users skip steps.
        $steps = &$steps_cached[$entity_type][$bundle];
        foreach ($steps as $key => $step) {
          // Hiding the skip button requires the attached
          // msnf-allow-users-to-remove-skip-button.patch
          if (isset($step->format_settings['instance_settings']['buttons']['skip'])) {
            unset($steps[$key]->format_settings['instance_settings']['buttons']['skip']);
          }
          // Allows editing from anywhere.
          $steps[$key]->format_settings['instance_settings']['skip_non_required'] = 1;
        }
      }
    }
  }
}