title: Caliburn element convention
body: <p>While trying to learn the source for GameLibrary sample application I saw a line like this:</p>
  
  <pre><code>ConventionManager.AddElementConvention&lt;Rating&gt;(Rating.ValueProperty, "Value", "ValueChanged");
  </code></pre>
  
  <p>Looked into the source of Caliburn but couldn't really understand what element conventions are.</p>
  
  <p>Can someone describe briefly please?</p>