Add METRO form hackery.

Not really sure where to comment on this... I'd like if we would only build out for the namespace with which we are concerned... May require a slightly more complex definition for the fields, to do it nicely?

```php
$elements = array(
  'cuny34thstreet' => array(
    'base_elements' => array(
      array('relatedItemFieldset', 'appearsIn'),
    ),
    'hier_elements' => array(
      array(
        'element' => array('notes'),
        'sub_elements' => array(
          array('displayLabel'),
        ),
      ),
    ),
  ),
  [...]
);

$map = function ($form, $definition) {
  $to_return = array();
  foreach ($definition['base_elements'] as $element_parents) {
    $to_return[] = &drupal_array_get_nested_value($form, $element_parents);
  }
  foreach($definition['hier_elements'] as $element_info) {
    $element = drupal_array_get_nested_value($form, $element_info['element']);
    foreach (element_children($element) as $key) {
      foreach ($element_info['sub_elements'] as $sub_element_info) {
        $to_return[] = &drupal_array_get_nested_value($element, $sub_element_info);
      }
    }
  }
  return $to_return;
};
$elements_to_enable = $map($form, $elements[$namespace]);
```
...  Though then again, this is starting to seem like premature optimization...  Shrug?