Change buttonGroup API to accept various information in data parameter

Change-Id: I0c3eb998d9be04fd1e7955b6c412277ec44755aa
diff --git a/dev/js/src/vc.js b/dev/js/src/vc.js
index b3a621a..6cd3c00 100644
--- a/dev/js/src/vc.js
+++ b/dev/js/src/vc.js
@@ -319,7 +319,7 @@
         ['action','button-view']
       );
       var that = this;
-      btn.add(loc.MINIMIZE, ['button-icon','minimize'], function () {
+      btn.add(loc.MINIMIZE, {'cls':['button-icon','minimize']}, function () {
         that.minimize();
       });
       this._element.appendChild(btn.element());