code: function _buildImageFields(data){
  
    var newUnits = [];
  
    for (var i = 0, len = data.length; i < len; i++){
  
      adUnit = data[i];
  
      // todo: create adUnit object to encapsulate this logic
      if ('images' in adUnit){
        if ('banner' in adUnit.images){
          adUnit.campaign_banner_url = adUnit.images.banner.url;
        }
        if ('icon' in adUnit.images){
          adUnit.campaign_icon_url = adUnit.images.icon.url;
        }
        if ('hq_icon' in adUnit.images){
          adUnit.campaign_hq_icon_url = adUnit.images.hq_icon.url;
        }
      }
  
      newUnits.push(adUnit);
    }
    return newUnits;
  }
docs: Fills some image fields with JSON data
  @param data The data coming from the server
  @returns processed data
  @private