[docs] Add docstrings for ElementTree module (issue 16954)

[merwok at netwok.org]

http://bugs.python.org/review/16954/diff/7390/Lib/xml/etree/ElementTree.py
File Lib/xml/etree/ElementTree.py (right):

http://bugs.python.org/review/16954/diff/7390/Lib/xml/etree/ElementTree.py#newcode1
Lib/xml/etree/ElementTree.py:1: """Lightweight XML support for Python
2.3 and later.
Duh yes it was minidom.  The fact that I don’t like the etree interface
made me lump it into the same mental category with minidom :)

http://bugs.python.org/review/16954/diff/7390/Lib/xml/etree/ElementTree.py#newcode27
Lib/xml/etree/ElementTree.py:27: And a number of child elements stored
in a Python sequence.
Well if there is an attribute named “children” it should be documented
like the other ones (and its English description would still be “child
elements”).

http://bugs.python.org/review/16954/