title: Delete item within owned collection using GWT RequestFactory
body: <p>I have a simple 1-n relationship (Product -> Item) mapped with RF EntityProxy. So,</p>
  
  <pre><code>ProductProxy extends EntityProxy {
      List &lt;ItemProxy&gt; getItems();
      void setItems(List&lt;ItemProxy&gt; items);
  }
  </code></pre>
  
  <p>I have also a Product Editor with a nested ListEditor for Items. Everything is working fine if I Add new a Item to product.items list or edit any of them (save successfully).</p>
  
  <p>However, If I remove one Item from the ProductProxy.getItems().remove(index) and try to save that product as a whole I noticed that when the object arrives on the server side, the item I've just removed is still within the collection.</p>
  
  <p>It seems to me that RF tries a lookup for the objects into the datastore (using the Locator) before injecting the new values into the service object.</p>
  
  <p>I need basically to be able to remove an Item within the collection and save the new (modified) collection into the Product object.</p>
  
  <p>Thanks!!</p>
  
  <p>PS. I'm using Objectify Ref&lt;> to keep that collections.</p>
  
  <p>Payload before sending request:</p>
  
  <pre><code> {"F":"web.app.gwt.shared.AppRequestFactory","O":[{"T":"kKv$zKrUQuvZDqvbc2XdTq6i1qU=","V":"NC4w","P":{"defaultOptions":[]},"S":"IjI5MiI=","O":"UPDATE"},{"T":"_dEu_lZqt6BooJQsjzBeHUf38EY=","V":"NC4w","S":"IjI5MCI=","O":"UPDATE"},{"T":"_dEu_lZqt6BooJQsjzBeHUf38EY=","V":"NC4w","S":"IjI4OSI=","O":"UPDATE"},{"T":"_dEu_lZqt6BooJQsjzBeHUf38EY=","V":"NC4w","S":"IjI5MSI=","O":"UPDATE"}],"I":[{"P":[{"T":"kKv$zKrUQuvZDqvbc2XdTq6i1qU=","S":"IjI5MiI="}],"O":"O4GgjqqjQkeFcxD6lGwHruEwO6U="}]}
  </code></pre>