title: ChangeListener on multiple Properties
body: <p>I have a model Tree of different POJOs containing several JavaFX <code>Property&lt;?&gt;</code> properties.</p>
  <p>I was now wondering on how to attach a <code>ChangeListener</code> to the top of the tree which is fired every time something in the object tree changes.</p>
  <p>I experimented a lot with custom Bindings and Invalidations but I think I am missing something here.</p>
  <p>The background here is, that I want to detect if the model needs to be saved or not. And I do not want to attach a change listener to every single property in that tree. There must be a better way.</p>