Introduce new config options in setup.cfg for PyScaffold and templates

[FlorianWilhelm]

We should set the following (copied over from setuptools github):

• long_description_content_type='text/x-rst; charset=UTF-8',

•    "Documentation": "https://setuptools.readthedocs.io/",
  

},```

and set the url to github and the documentation to our homepage. This way we should also see the nice Github statistics on PyPI as with setuptools.

[FlorianWilhelm]

I just activated these settings for configupdater and it works great. Check it out on PyPI. One important thing though, one must use twine to upload to PyPI for this to work!

[FlorianWilhelm]

Done in 499fcd1. I guess these settings are not important enough to define them in the update procedure.