title: How to add user defined checkbox at JQGrid header
body: <p>Has try as below</p>
  
  <pre><code>jqGrid({
  datatype: 'json',
  colNames: ["&lt;input type='checkbox' name = 'chkAllOutputField'/&gt;", "other columns" ]
  </code></pre>
  
  <p>check box is shown on header , but will not be checked/unchecked no matter how you click it.</p>
  
  <p>How can I make it checked/unchecked by clicking</p>