code: private String unescapeHtml(Object content) {
          return content != null ? content.toString().replace("&lt;", "<").replace("&gt;", ">") : "";
      }
docs: Unescapes the content of a rule.
  
  TODO do better, or even better add a partget(Original|Raw)Content() to
  asciidoctor
  
  @param content
  The content of a rule.
  @return The unescaped rule