title: how to add dynamic column in ng-table using complex object or json?
body: <p>i have following code for ng-table:<a href="http://plnkr.co/edit/oTxkmtAwt22gtO2JDPg4?p=preview" rel="noreferrer">see plunker</a></p>
  
  <pre><code>var app = angular.module('main', ['ngTable']).
      controller('DemoCtrl', function($scope, $filter, ngTableParams) {
          var data = [{name: "Moroni", age: 50,address:{coun:'USA',state:'sd'}},
              {name: "Tiancum", age: 43,address:{coun:'UK',state:'sda'}},
             ];
          $scope.columns = [
              { title: 'Name', field: 'name', visible: true, filter: { 'name': 'text' } },
              { title: 'Age', field: 'age', visible: true },
              { title: 'country', field: 'add', visible: true }
          ];
          $scope.tableParams = new ngTableParams({
              page: 1,            // show first page
              count: 10,          // count per page
              filter: {
                  name: 'M'       // initial filter
              }
          }, {
              total: data.length, // length of data
              getData: function($defer, params) {
                  // use build-in angular filter
                  var orderedData = params.sorting() ?
                          $filter('orderBy')(data, params.orderBy()) :
                          data;
  
                  $defer.resolve(orderedData.slice((params.page() - 1) * params.count(), params.page() * params.count()));
              }
          });
      })
  </code></pre>
  
  <p>and HTML:</p>
  
  <pre><code>       &lt;tr ng-repeat="user in $data"&gt;
              &lt;td ng-repeat="column in columns" ng-show="column.visible" sortable="column.field"&gt;
                  {{user[column.field]}}
              &lt;/td&gt;
         &lt;/tr&gt;
  </code></pre>
  
  <p>i have to display name age and country in column. but using this code i can see name ,age and <code>address</code> object not country. please suggest me how to display only country or state. </p>