use title instead of node id for item label

By default, when using the Views plugin to create the json feed, the nid is used as the label for each item record. The label is used within the Exhibit framework for a few things, most notably for me in the MapView infoWindow when more than one marker has the same coordinates. In this case, and in most cases, I think the label should be more user-friendly and descriptive.

I got around this by editing views_plugin_style_exhibit_json.inc

$items[$row->$base_field] = array_merge(array('label' => $row->$base_field, 'type' => $this->view->base_table), $item);

to

$newlabel = $row->$base_field;
if ($item['title_1']) {
$newlabel = $item['title_1'];
   if (strlen($item['title_1']) > 50) $newlabel = substr($item['title_1'],0,50)."...";
}
$items[$row->$base_field] = array_merge(array('id'=>$row->$base_field, 'label' => $newlabel, 'type' => $this->view->base_table), $item);

In the above, I always add two node Title fields to the View, the first one "title" is linked to the node, and the second "title_1" is not. The second field "title_1" is used as the label. Also, my titles were kind of long and blew up the MapView infoWindow bubbles, so I restricted the length of the strings to 50 characters. This is certainly not necessary and probably should be best done though a javascript function in Exhibit.

It would be nice that for each view/feed, you can specify (in the Views UI) which field you to use as the label and, optionally, the string length limit.