Better i/o for editing metadata in preview

Signed-off-by: Justin Georgi <justin.georgi@gmail.com>

includes/GlModelHooks.php

@@ -76,11 +76,18 @@ class GlModelHooks {
         $previewViewer = $mvTransform->toHtml([ 'preview' => true]);
 
         $addButtonAttr = array(
-            'class' => 'AddHotspot',
+            'class' => 'preview-button AddHotspot',
             'onclick' => 'readyAddHotspot()'
         );
+
+        $readButtonAttr = array(
+            'class' => 'preview-button ReadHotspots',
+            'onclick' => 'readMetadata()'
+        );
+
         $addHsButton = array(
-            Html::rawElement('button',$addButtonAttr,'Add a new hotspot')
+            Html::rawElement('button',$addButtonAttr,'Add a new hotspot'),
+            Html::rawElement('button',$readButtonAttr,'Update hotspots')
         );
 
         $previewHTML = Html::rawElement('div',NULL,$previewViewer.implode($addHsButton));