title: Deserializing ImmutableList using Gson
body: <p>I'm using quite a few immutable collections and I'm curious how to deserialize them using Gson. As nobody answered and I've found the solution myself, I'm simplifying the question and presenting my own answer.</p>
  
  <p>I had two problems:</p>
  
  <ul>
  <li>How to write a single <code>Deserializer</code> working for all <code>ImmutableList&lt;XXX&gt;</code>?</li>
  <li>How to register it for all <code>ImmutableList&lt;XXX&gt;</code>?</li>
  </ul>