title: HelpPage xml documentation when controllers or models in different assembly
body: <p>Using the new webapi 2.1 bits. For some reason when I open the help page no description details appear for any properties e.g.</p>
  
  <pre><code>/// &lt;summary&gt;
  /// Some summary that shows correct
  /// &lt;/summary&gt;
  [DataContract]
  public class MyClass
  {
  
      /// &lt;summary&gt;
      /// Display something.....
      /// &lt;/summary&gt;
      [DataMember(Name = "Great")]
      public string MyGreatProperty { get; set; }
  </code></pre>
  
  <p>When I open the help page I can see the summary "Some summary that shows correct" however for the properties of this model none of the summaries are showing up.</p>
  
  <p>Does webapi 2 not support descriptions on a property?</p>