Set a default value for arguments of cubicweb.cwctl:run()
This will help making a console script entry point from this to get rid
of the custom installation of scripts in setup.py.
Accordingly, update all calls of this function.
[pkg] Drop custom install_lib command and use include_package_data instead
The custom install_lib command appeared to be meant to install package
data, as declared in __pkginfo__.py. Let's rely on setuptools'
include_package_data[1] option to handle this.
[1]: http://setuptools.readthedocs.io/en/latest/setuptools.html#including-data-files