title: Automatically update xcore/ecore attribute
body: <p>In an Eclipse plug-in I have a custom model defined in an <code>.xcore</code> file and it contains this <code>EClass</code> definition:</p>
  
  <pre><code>class Person {
      String name
      String surname
  
      Date dateUpdated
  }
  </code></pre>
  
  <p>My question here is: if I manually edit any of the attributes of an instance of this class (in the Eclipse properties view), is there a way to automatically update the <code>dateUpdated</code> attribute? </p>
  
  <p>I know that this can be done with an <code>EContentAdapter</code>, but is there an easier way to define this in the Xcore file or through some other mechanism?</p>