title: ItemsControl start at CurrentPosition = 0 instead of -1
body: <p>I am making a custom control which is a FlipView. In it's control template, there exists a ContentControl which binds to <code>Items.CurrentItem</code> and there is a next button and a previous button which will do <code>Items.MoveCurrentToNext()</code> and vice versa. So far, so good.   </p>
  
  <p>My problem is that at the start, the <code>Items.CurrentItem</code> is <code>null</code> so the flipview is empty. I want it to show the first item in its Items collection.  </p>
  
  <p>The solution I am using currently is deriving from <code>Selector</code> and setting <code>IsSynchronizedWithCurrentItem = true</code> and setting <code>SelectedIndex = 0</code> in the constructor. This works, but is there a better way to do it? I don't need the functionality of a selector except for this workaround.  </p>
  
  <p><code>this.Items.MoveCurrentToPosition(0);</code> doesn't work either. It does nothing :/</p>