title: Rally 2.0 SDK API - Comparing dateTime types in a Filter Query
body: <p>I would like to filter my userStories by comparing the AcceptedDate and the Iteration.EndDate. Something like AcceptedDate > Iteration.EndDate. Is it possible?</p>
  
  <p>I tried the following but as i supposed, it didn't work:</p>
  
  <pre><code>var storiesQuery = Ext.create('Rally.data.WsapiDataStore', {
      model: 'UserStory',
      fetch: ['Iteration', 'AcceptedDate'],
      filters: [  
          {
              property: 'Iteration.EndDate',
              operator: '&lt;',
              value: 'AcceptedDate'
          },
          {
              property: 'ScheduleState',
              operator: '=',
              value: 'Accepted'
          }, 
          {
              property: 'DirectChildrenCount',
              operator: '=',
              value: '0'
          },
          {
              property: 'AcceptedDate',
              operator: '&lt;',
              value: 'LastMonth'
          }
      ]
  });
  </code></pre>
  
  <p>Thanks.</p>