title: How can I get a reference to the TFS WorkItem in a WorkItemChangedEvent?
body: <p>Seems like this would be super simple, but I'm struggling to find what I need.</p>
  
  <p>I'm implementing a TFS 2013 event handler and simply want to get a reference to the Work Item that raised the change event. It seems easy enough to get the title, but I can't find a property or method in the event signature objects that gives me either a reference to the WorkItem object or the information I'd need to go query it (e.g. the ID).</p>
  
  <pre><code>public EventNotificationStatus ProcessEvent(
           TeamFoundationRequestContext requestContext, 
           NotificationType notificationType, 
           object notificationEventArgs, 
           out int statusCode, 
           out string statusMessage, 
           out ExceptionPropertyCollection properties)
      {          
          var ev = notificationEventArgs as WorkItemChangedEvent;
          string WorkItemTitle = ev.WorkItemTitle; /* easy enough */
  
          /*********** need help with this bit *********/
          int ChangedWorkItemID = ???
                OR
          WorkItem ChangedWorkItem= ???
      }
  </code></pre>
  
  <p><strong>Note:</strong> this code has been stripped down to bare bones to make it easier to read and focus on the problem at hand.</p>