Implements xml_form_builder_definition_alter to alter access permission ...

...to tab elements for zoomaps and murrayhill namespaces.  The elements only need to be set for the default index of the tab panel and once the form is rendered the access to other fields will be inherited to all tab panels.

Requires update to the islandora xml form builder module:  Pull request that adds the hook: https://github.com/Islandora/islandora_xml_forms/pull/159
Why not just do something like:
```php
function metrodora_form_alter(&$form, &$form_state) {
  // Figure out if we should actually perform the alter (probably checking the form ID and the name (as XML Form should have, somewhere?)).
  // Iterate over stuff in the tabs...
  if ($namespace == 'murrayhill') {
    foreach ($form['subjects'] as &$subject) {
      $subject['cartographicsFieldset']['#access'] = 1;
      $subject['cartographicsFieldset']['coordinates']['#access'] = 1;

      // Grant access to hierarchicalGeographicFieldset and citySection field.
      $subject['hierarchicalGeographicFieldset']['#access'] = 1;
      $subject['hierarchicalGeographicFieldset']['citySection']['#access'] = 1;
    }
  }
}
```