Renamed output* methods to xml*
Added test cases for ClassifierXml.Writer
Tidied up the xml test strings in TestWriter
Added methods to write out a complete XML file.

Also added a dodgy hack to work around the Python ElementTree XML library not handling elements/attributes which aren't prefixed with the default namespace.
Started adding more XML output tests...this is a temporary commit
Fix up XML output tests
Added dodgy hack to override unnecessary namespace prefixes