Add mechanism to get number of attributes on an Element
Add revised version of the JDOMStreamReader together with some implementation details for JDOM integration, and a round-trip test
Merge branch 'stream_reader' of github.com:gburgett/jdom into stream_reader

Conflicts:
	core/src/java/org/jdom2/jaxb/JDOMStreamReader.java
	test/src/java/org/jdom2/test/cases/output/TestStAXWriterReader.java