title: combobox: send values of valueField and displayField to server in update
body: <p>Consider an app with a grid, a form and a window.</p>
  
  <p>If I select a grid row the record data (detail) is displayed in form (binding).</p>
  
  <p>With dblclick event in grid row a window with form is displayed to update the record, and fields are filled (binding).</p>
  
  <p>The form on window has a combobox that has a store and the value of the field to update is filled by binding.</p>
  
  <p>My issue:</p>
  
  <p>I need to send combobox valueField and displayField to server in update (the id and cars value) simultaneously. </p>
  
  <p>Is there any way to do this directly with a combobox config or adding, in some way, another bind/value?</p>
  
  <pre><code>xtype: 'combobox',
  fieldLabel: 'myField',
  name:'id', 
  bind: {
      store: '{mystore}',
      value: '{record.id}' //load value from record to update and bind (to display in grid and form)
  },
  displayField:'cars',
  valueField:'id',
  queryMode: 'local',
  </code></pre>
  
  <p>EDITED: </p>
  
  <p>One solution I usually use, which requires the use of a method or event, is:</p>
  
  <pre><code>    var values = myForm.getValues();
      var comboValue = Ext.ComponentQuery.query('#mycomboItenmId')[0].getRawValue();
  
      var objCombosValue = {
           'combo_value': comboValue
       }
  
       var allValues = Ext.Object.merge(values, objCombosValue);
  
       record.set(allValues);
  
       store.sync({})
  </code></pre>
  
  <p>Is there any pure binding solution for this?</p>