setup.py: migrate from distutils to setuptools

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
Rules: new module

This is where I expect to put the Rules hierarchy processing.

For now I just implement the get_global_rules_filepath function which
returns the file location of the global outrules.d/base.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
Rules: get_global_rules_filepath: distutils-r1 trouble

A complex interaction between setuptools and distutils-r1 (no
gentoo bug filed yet) seems to prevent the standard setuptools
recipe for retrieving project-level install-data files
programmatically from working.  So, hardcode the file-location
where portage is going to install them relative to EPREFIX
and grab EPREFIX from portage.const (we will get portage
dependencies later anyhow), in order to find our project's global
data files location.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>