title: Cesium proper way to destroy viewer
body: <p>How in Cesium to destroy viewer?</p>
  
  <p>I have few points in my viewer.entities and a model. By user clicking "Hide Cesium viewer" button - I perform</p>
  
  <pre><code>viewer.entities.removeAll();
  viewer.destroy();
  </code></pre>
  
  <p>But by user clicking "Show Cesium viewer" button - I perform all the same adding points and model. And I see points added, but model - not.</p>
  
  <p>So I think that i have missed something during destroying.</p>