implemented saving/loading for groups

app/node/factory.h

@@ -61,6 +61,7 @@ public:
     kTimeRemapNode,
     kSubtitleBlock,
     kShapeGenerator,
+    kGroupNode,
 
     // Count value
     kInternalNodeCount
@@ -87,6 +88,8 @@ public:
 private:
   static QList<Node*> library_;
 
+  static QVector<int> hidden_;
+
 };
 
 }