Implement attributes granular diff if elements have no childs and equal names

Please look at DEV-tests/node_attr_change.orig.xml DEV-tests/node_attr_change.xml and DEV-tests/node_attr_change.DM.xml
as produced result diff.

File DEV-tests/node_attr_change.DM-example.xml contain some investigation which had been tried to be implemented.
try2 seams much compact and preferable for my own use cases (mostly document without namespaces in attributes)
but implementing proper handling of NS possible and horrible. Last example used.

NO any implementation of merge attempted at all! But I could try to do so if that desired.