[pkg] Drop NO_SETUPTOOLS option
setuptools is the defacto standard nowadays. The only place where
NO_SETUPTOOLS option was used is during packaging (RPM, Debian) and even in
this context, it seems that setuptools is the way to go
(see https://wiki.debian.org/Python/LibraryStyleGuide).
usr/lib/python2*/*-packages/cubicweb/entities/
usr/lib/python2*/*-packages/cubicweb/ext/
usr/share/cubicweb/cubes/
usr/lib/python2*/*-packages/cubicweb/*.py