Hide internal API methods

[SomeSourceCode]

Description

Some methods that are supposed to be used exclusivly by the API shouldn't be accessible for the user. Examples are Node#setParent(Parent), Node#setScene(Scene), Scene#setGui(Gui), or Gui's methods for managing DirtyFlags. Those methods being publicly accessible could lead to unexpected behavior of the API.

Potential Solution

This could be done via NodeHelper, SceneHelper, GuiHelper, etc. classes. The API could then call these internal methods from these classes:

NodeHelper.setParent(node, parent);
NodeHelper.setScene(node, scene);
SceneHelper.setGui(scene, gui);