• ElementHolder can inherit onTick to do something when it ticks. Instead, I suggest adding a callbacks on tick to ElementHolder or VirtualElement. This is useful when writing in the Builder or DSL style.
• When ElementHolder's VirtualElements are riding on Entity, notifyElementsOfPositionUpdate is called every tick, so trembling occurs. So I suggest adding a property to determine whether to call notifyElementsOfPositionUpdate or not.
• To check if a particular ElementHolder is attached to a target, create and use a class that inherits ElementHolder, call the ElementHolders using impl, and then check if an instance of that class is included. So, I suggest to make sure ElementHolder can be identified by String or Identifier, and api can check if a specific ElementHolder is already attached to the target.

Added way to disable sending of positions to client. Not sure if I want to go with other two