* @param node XML description.
* @param version XML state version.
* @param notes A list to which is added descriptions of any non-critial warnings / messages.
* @return Content object, or 0 if no content was recognised in the XML.
*/
shared_ptr<Content>
* @param node XML description.
* @param version XML state version.
* @param notes A list to which is added descriptions of any non-critial warnings / messages.
* @return Content object, or 0 if no content was recognised in the XML.
*/
shared_ptr<Content>