title: put two named instances in MEF
body: <p>In Unity I would do something like this:</p>
  
  <pre><code>Container.RegisterType&lt;MyClass&gt;("MyNamedInstance", new ContainerControlledLifetimeManager());
  </code></pre>
  
  <p>Then I could put multiple instances of the same class in.  </p>
  
  <p>How can I do this in MEF?</p>