title: how to get value entered in UI created with the new HtmlService
body: <p>I can get/access the value of the UI elements using,</p>
  
  <pre><code>e.parameter.elementname or app.getElementById(id) 
  </code></pre>
  
  <p>if i create UI using UiApps or GUI builder like,</p>
  
  <pre><code>app.add(app.loadComponent("MyGui"));
  app.getElementbyId('textbox1').setText("Hi");
  </code></pre>
  
  <p>If i use, HtmlService.createHtmlOutputFromFile('myPage'); 
  How can i get the values entered in the html form - elements ?</p>