title: displaying nested json in ag-grid
body: <p>I am using Angular Grid (ag-grid) to display data. i am trying to display nested json data in my angular grid. but i was unsuccessful.</p>
  
  <p>below is the sample json data and colDefs. please suggest that why dot operator is not working unlike jqgrid, to map grid columns with nested json fields.</p>
  
  <pre><code>var app = angular.module('myApp', ['ngGrid']);
  app.controller('MyCtrl', ['$scope', '$http',
  function($scope, $http) {
  $scope.myData = [{
  "defaultColumns1": {"region":"PA"},
  "defaultColumns2": {"LocationName": "loc1",
  "LegalName": "legName1"
  }
  },
  {
  "defaultColumns1": {"region":"PB"},
  "defaultColumns2": {"LocationName": "loc2",
  "LegalName": "legName2"
  }
  }];
  
  $scope.gridOptions = {
    data: 'myData',
    columnDefs: [{
      field: 'defaultColumns1.region',
      displayName: 'Region'
    }, {
      field: 'defaultColumns2.LocationName',
      displayName: 'Location',
      headerGroup: 'address'
    }, {
      field: 'defaultColumns2.LegalName',
      displayName: 'Legal Name',
      headerGroup: 'address'
    }],
    enableColumnResize: true,
    groupHeaders : true
  }
  }]);
  </code></pre>
  
  <p>index.html</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html ng-app="myApp"&gt;
  
  &lt;head lang="en"&gt;
  &lt;meta charset="utf-8" /&gt;
  &lt;title&gt;Custom Plunker&lt;/title&gt;
  &lt;link  rel="stylesheet" href="../dist/ag-grid.css" /&gt;
  &lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.2/jquery.js"&gt;   &lt;/script&gt;
  &lt;script src="http://code.angularjs.org/1.2.15/angular.js"&gt;&lt;/script&gt;
  &lt;script  src="../dist/ag-grid.min.js"&gt;&lt;/script&gt;
  &lt;link href="//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css"   rel="stylesheet" /&gt;
  &lt;link rel="stylesheet" type="text/css" href="style.css" /&gt;
  
  &lt;script type="text/javascript" src="main.js"&gt;&lt;/script&gt;
  &lt;/head&gt;
  
  &lt;body ng-controller="MyCtrl"&gt;
  &lt;div class="gridStyle" ag-grid="gridOptions"&gt;&lt;/div&gt;
  &lt;/body&gt;&lt;/html&gt;
  </code></pre>