/// <summary>
 /// Adds a ValueController to the ValueControllerChain.
 /// </summary>
 /// <param name="layer">The layer of the ValueController</param>
 /// <param name="valueController">The ValueController.</param>
 /// <remarks>ValueController on the same layer are started simultaneously.</remarks>
 public void AddValueController(int layer, ValueController <T> valueController)
 {
     this.AddValueController(layer, valueController, null);
 }