Merge xmpp.py 4.1 simplexml.py

See #3694


 * WARNING! Incompartible change! Now newtag=n.T.newtag do not creates new tag
but only returns existing one (if possible). If you need to create tag use
either .NT. method or attribute set (i.e. n.T.newtag=something).

 * Added CDATA extracting method to xml node.

 * added xmlns safety check

 * Fixed node attribute deletion with "del node[attr]" syntax.

 * Ordering fix for when addChild and addData are used on the same node (may increase memory usage, might need to watch for that)

 * Fixes for children node fetching, still not perfect, but much better