Fixed init of Group (actually should NOT init its children nodes).

Ensure Nodes deletetion is done.

Mesh.h

@@ -22,6 +22,7 @@ public:
     void init () override;
     void draw (glm::mat4 modelview, glm::mat4 projection) override;
     void accept (Visitor& v) override;
+//    void update (float dt) override;
 
     inline std::string getResource() const { return resource_; }
     inline std::string getTexture() const { return texturefilename_; }