Added more documentation for serialization.

   * The constructor pushes it's own content handler (the XmlHandler class) on the reader

   * to allow parsing to continue with this object. Note the push of the content handler

   * does not return until the XML is parsed, specifically the push of the content handler

   * calls XmlHandler::startElement() for the handler just pushed.  If a contained object

   * calls XmlHandler::startElement() for the handler just pushed. (Actually the behavior

   * of XmlStackedHandlerReader::pushContentHandler() varies - if there are no contentHandlers

   * on the content handler stack when it is called it returns immediately and parse()

   * must be called to start parsing.  If there is a content handler already on the stack

   * the push results in a call to startElement() and it does not return until the

   * corresponding end element.)

   *

   * If a contained object

   * is found while parsing the XML, the constructor for the contained object that takes a

   * XmlStackedHandlerReader as a parameter is called.  This will result in the contained

   * object pushing it's content handler and parsing the relevant XML. When the constructor

  }

  /**

   * @brief Push a contentHandler and maybe continue parsing...

   *

   *   Push a contentHadler on the content handler stack.  If there are currently

   *   no other handlers on the stack that is all that happens.

   *

   *   If there are other content handlers on the stack it is assumed that

   *   a XML file is being processed and processing continues by calling

   *   startElement() of the newly pushed handler.  In this case

   *   pushContentHandler() will not return until the element has been

   *   fully processed.

   *

   */

  void XmlStackedHandlerReader::pushContentHandler(XmlStackedHandler *newHandler) {

    XmlStackedHandler *old = topContentHandler();