title: ExtJs, how to send JSON on store.load() using POST method
body: <p>I need to send JSON object during read operation on store. Headers and method are set correctly.</p>
  
  <pre><code>var proxyDefinition = {
      type : 'rest',
      api : {
          read : '/some/url'
      },
      actionMethods : {
          create  : 'POST',
          read    : 'POST',
          update  : 'PUT',
          destroy : 'DELETE'
      },
      reader : {
          type : 'json'
      }        
  };
  
  var store = Ext.create('Ext.data.Store', {
      proxy : proxyDefinition,
      model : 'SomeModel'
  });
  
  // this needs to send JSON
  store.load({
      params : {
          filter: [] // some filtering rules
      }
  });
  </code></pre>
  
  <p>Problem is that POST body is sent as url encoded query string, not JSON object with property "filter".</p>
  
  <p>ExtJs version 4.2.2</p>