code: function WixSDK(rootPath, manifest, output) {
  
      this._rootPath = rootPath;
      this._manifest = manifest;
      this._output = output;
  
      this._existing_ids = {};
  }
docs: Creates WixSDK object.
  @param {String} rootPath Root path for project
  @param {Manifest} manifest Web manifest
  @param {OutputIface} output Output
  @constructor