code: function rename(oldPath, newPath, callback) {
          appshell.fs.rename(oldPath, newPath, _wrap(callback));
      }
docs: Rename the file or directory at oldPath to newPath, and call back
  asynchronously with a possibly null FileSystemError string.
  
  @param {string} oldPath
  @param {string} newPath
  @param {function(?string)=} callback