fulfil setuptools features for distutils2

by higery for Python Software Foundation

Distutils2 is the new, improved version of the Python Distribution Utilities, a library used to package, distribute, build and install Python projects. It will be as a substitute of current setuptools, but it’s still in its early stage. This project is supposed to fill the gap for setuptools users that want to move to packaging in two aspects: 1) add the ‘develop’ command for Distutils2; 2) add the automatic script creation function; 3) perfect the extensions project.