* Fixed a bug in 'rdlibrary/audio_cart.cpp' where the 'Conductor'
failed to be imported from RDXL chunks.
* Added a 'songId' field to the cart metadata XML.
* Added rdxml_parse_test(1) in 'tests/'.
* Added a RDCart::readXml()' method in 'lib/rdcart.cpp' and
'lib/rdcart.h'.
* Fixed a typo in the 'averageSegueLength' field in the 'RDCart::xml()'
method in 'lib/rdcart.cpp'.
* Removed the 'validity' field from the output of the 'RDCart::xml()'
method in 'lib/rdcart.cpp'.
* Removed the 'validity' and 'localCounter' fields from the output
of the 'RDCut::xml()' method in 'lib/rdcut.cpp'.