Remove parent disabled/treeVisible listeners

`Node` adds InvalidationListeners to its parent's `disabled` and `treeVisible` properties and calls its own `updateDisabled()` and `updateTreeVisible(boolean)` methods when the property values change.

These listeners are not required, since `Node` can easily call the `updateDisabled()` and `updateTreeVisible(boolean)` methods on its children, saving the memory cost of maintaining listeners and bindings.