code: public static String getRootDirURI(File parentDir) {
          String pathAsString = parentDir.getAbsolutePath() + System.getProperty("file.separator") + Names.EKSTAZI_ROOT_DIR_NAME;
          return new File(pathAsString).toURI().toString();
      }
docs: Returns absolute path to .ekstazi director (URI.toString). Note
  that the directory is not created with this invocation.
  
  @param parentDir
  Parent directory for .ekstazi directory
  @return An absolute path (URI.toString) that describes .ekstazi directory