code: public JenkinsServer createFolder(String folderName, Boolean crumbFlag) throws IOException {
          return createFolder(null, folderName, crumbFlag);
      }
docs: Create a folder on the server (in the root)
  
  @param folderName name of the folder.
  @param crumbFlag <code>true</code> to add <b>crumbIssuer</b>
  <code>false</code> otherwise.
  @throws IOException in case of an error.