title: Proper syntax to read and write byte array in Cap'n Proto?
body: <p>Let's say I have an array:</p>
  
  <pre><code>struct UUID
  {
      char data[16];
  };
  </code></pre>
  
  <p>And I have it like so in the schema:</p>
  
  <pre><code>struct UUID
  {
      value @0 : Data;
  }
  </code></pre>
  
  <p>What's the proper way to read and write this field? It looks like I should be able to wrap a <em>capnp::Data::Reader</em> around the array and use the builder's setValue(), but the syntax is really non-obvious.</p>
  
  <p>The other way is also somewhat mysterious. How do I populate the array when deserializing? My current approach involves a memcpy, but I assume there's a Cap'n Proto way to do it.</p>