selected_data -> data to make the transition of old code easier. Old code can be simply converted by adding () after data

Former-commit-id: 02c8268a61

tutorial/106_ViewerMenu/main.cpp

@@ -65,7 +65,7 @@ int main(int argc, char *argv[])
   };
 
   // Plot the mesh
-  viewer.selected_data().set_mesh(V, F);
+  viewer.data().set_mesh(V, F);
   viewer.launch();
 }
 #endif