title: extjs stateful grid remove sort
body: <p>I have a problem with statefull grid. I do not want to save the sort state but I do want to save all other options (column position, column width, grouping etc.)</p>
  
  <p>For now I have tried this with stateEvents option, but it saves whole state of grid when the even fires.</p>
  
  <p>Is there any option to exclude sort state from saving??</p>
  
  <p>Part of the grid config:</p>
  
  <pre><code>this.gridPanel = new Ext.grid.GridPanel({
                  id:'grid'+this.id,
                  region:region,
                  layout:'fit',
                  stateful:true,
                  stateEvents: ['columnmove', 'columnresize', 'groupchange', 'bodyresize'],
                  loadMask:true,
                  split:true,
                  store: this.stores['root'+this.id],
                  cm: this.getRootColumnModel(),
                  sm: this.getRootSelectionModel(),
  </code></pre>