Get more Python package data when scanning setup.cfg

[JonoYang]

In Python packages, the setup.py file can contain origin info for a package. We can determine what the license, copyright holder, homepage and download URLs, as the package owner/maintainer declared it. However, some Python packages (like scancode-toolkit and other nexB projects) declare all of the package info and whatnot in setup.cfg, then let setuptools handle everything else. It does not seem that we get license or holder information when we do a Package scan on a setup.cfg, we only get the declared dependencies.

It would be convenient to be able to get more Package information from setup.cfg when scanning Python packages.