title: Extjs cache JSON request
body: <p>Hi i'm using Extjs and i have built a grid with editable cells. One of this cells must be a combobox that takes its options from a script that generates the json data. The code for the grid and for the combobox-cell-editor works but i want that the json request to the script is cached after the first time, is it possible?</p>
  
  <p>I write some code, this is the part where i declare the combobox column in the grid constructor:</p>
  
  <pre><code>{
      dataIndex:"authors_name",
      id:"authors_name",
      header:"Authors",
      editable:true,
      sortable:true,
      editor:{
          xtype:"combo",
          allowBlank:false,
          editable:false,
          forceSelection: true,
          displayField: 'authors_name',
          valueField: 'authors_id',
          store:new Ext.data.JsonStore({
              proxy:new Ext.data.HttpProxy({
                  //This is the json request to cache
                  url: 'index.php?load=authors'
              }),
              root: 'items',
              fields: ['authors_name','authors_id']
          })
      }
  }
  </code></pre>