code: public static List<String> getProperties(String prefix) {
          List<String> res = new ArrayList<>();
          prefix += ".";
          for (int i = 1; ; i++) {
              String prop = p(prefix + i);
              if (prop == null)
                  return res;
              res.add(prop);
          }
      }
docs: Return all numbered properties with a prefix. For instance if there is a file:
  <pre>
  prop.1=one
  prop.2=two
  </pre>
  
  .. and this method is called:
  <pre>
  List<String> props = AppConfig.getProperties("prop");
  </pre>
  then the resulting list will have all properties starting from <code>prop</code>.
  This method presumes consecutive numbers in the suffix.
  
  @param prefix    prefix of numbered properties.
  @return list  of property values.