title: how to find column index using dataIndex Extjs 4
body: <p>Well in ExtJS 3 i used the following code:</p>
  
  <p><code>grid.getColumnModel().findColumnIndex("Tasks")</code></p>
  
  <p>I tried finding it on the api docs, but no luck...so how is ir possible that i can find the column index of the grid by the dataIndex of the column or the header name of that column.</p>