title: Extjs drag and drop single item on grid with checkbox model
body: <p>I modified the following example code to checkbox model.  Here is the link
  <a href="http://docs.sencha.com/extjs/4.2.1/#!/api/Ext.grid.plugin.DragDrop" rel="nofollow">http://docs.sencha.com/extjs/4.2.1/#!/api/Ext.grid.plugin.DragDrop</a></p>
  
  <p>Two questions, first:<br>
  When dragging an item, all the selected items are being moved too. How to drag only one item each time?</p>
  
  <p>Another question:<br>
  When dragging an item, it is forced to become selected. How to make it remain state unchange? (keep unselected when it is unselected before the drag, and vice versa)</p>
  
  <p>And I am using version 4.2.1.</p>
  
  <p>Here is the code modified from the given example:  </p>
  
  <pre><code>Ext.onReady(function () {
      Ext.create('Ext.data.Store', {
          storeId: 'simpsonsStore',
          fields: ['name'],
          data: [
              ["Lisa"],
              ["Bart"],
              ["Homer"],
              ["Marge"]
          ],
          proxy: {
              type: 'memory',
              reader: 'array'
          }
      });
  
      Ext.create('Ext.grid.Panel', {
          store: 'simpsonsStore',
          selModel: {mode: 'SIMPLE'}, //added
          selType: 'checkboxmodel', //added
          columns: [{
              header: 'Name',
              dataIndex: 'name',
              flex: true
          }],
          viewConfig: {
              plugins: {
                  ptype: 'gridviewdragdrop',
                  dragText: 'Drag and drop to reorganize'
              }
          },
          height: 200,
          width: 400,
          renderTo: Ext.getBody()
      });
  });
  </code></pre>
  
  <p>Thank you!</p>