title: Extjs 4 create dynamic grid
body: <p>I am creating grid panel in extjs4 with below requirement :</p>
  
  <ul>
  <li>Coulmn name and column data should take from json file.</li>
  <li>Number of column should increase/decrease as per data exist in json.</li>
  </ul>
  
  <p>I dont want to use any extension /plugin to do this, please suggest any pointer in extjs4.</p>
  
  <p>Thanks,</p>
  
  <p>Pravin </p>