Support for DOM and other external tree models

I have tested the JDOM interface more thoroughly at this release than previously, and this has revealed some problems. I have fixed the most serious of these. Most of the failed tests relate to the use of the namespace axis, and since the namespace axis is not mandatory in XPath 2.0, I have withdrawn support for this axis with the JDOM interface.

Shortly before Saxon 7.5 was finished, JDOM beta 9 became available (the first new release for a year). I tested Saxon 7.5 with the new release without problems.