title: INotifyPropertyChange does not update converter-based values?
body: <p>I have an image with source set by a <code>ValueConverter</code>:</p>
  
  <pre><code>&lt;Image Source="{Binding Converter={StaticResource siConv}}" Width="16" Height="16"/&gt;
  </code></pre>
  
  <p>When the bound object raises a <code>PropertyChanged</code> event (from <code>INotifyPropertyChanged</code>), the image does not change.  I assume it is because WPF doesn't know what fields the converter looks at.</p>
  
  <p>How do I tell WPF to rebind/rerun this converter when a certain property changes?</p>