code: public Map<String, List<String>> listCommands() {
          Map<String, List<String>> result = new HashMap<String, List<String>>();
          for (String cat : restMetadataJson.keySet())  {
              JsonObject commands = restMetadataJson.getJsonObject(cat);
              List<String> names = new ArrayList<String>();
              for (String commandName: commands.keySet()) {
                  names.add(commandName);
              }       
              result.put(cat, names);
          }
          return result;
      }
docs: Retrieve the map of commands keyed by service name
  @return map of commands