first contribution towards implementing #57.

Note: We might want to generate the internal structures UA_NodeSet,
UA_NodeSetAliases and UA_NodeSetAlias with @jpfr's plugin for
generate_builtin.py
deactivated textHandler and some refactoring.

Sometimes in the making I changed the logic of the XML_Stack and forgot
about the textHandler which needs to be redesigned. To make it possible
to finish with all the other stuff I temporarely disabled the
textHandler.
Merge remote-tracking branch 'upstream/master'
Merge pull request #63 from uleon/master

recent work on xml2ns