[toward-py3k] rewrite __cmp__ (closes #2715115)
In Python 3k `__cmp__` special method is no longer supported. So we split
it in `__lt__` and `__eq__`.
details on Python3k behavior here:
http://docs.python.org/3.0/whatsnew/3.0.html#ordering-comparisons
debian/tmp/usr/lib/PY_VERSION/site-packages/cubicweb/web usr/lib/PY_VERSION/site-packages/cubicweb
debian/tmp/usr/share/cubicweb/cubes/shared/data usr/share/cubicweb/cubes/shared
debian/tmp/usr/share/cubicweb/cubes/shared/wdoc usr/share/cubicweb/cubes/shared