setup.py: Add more metadata useful for PyPI

Description

• setup.py: List useful links using project_urls

• setup.py: Specify minumum python vresion using python_requires

  python_requires is the new way of specifying requirements for python version, as documented @ https://packaging.python.org/guides/distributing-packages-using-setuptools/#python-requires.

  This will also make this requirement appear nicely on the PyPI project page.

• setup.py: Add project classifiers

  PyPI will use these classifiers to categorize projects while searching or browsing. Full list of classifiers can be found at https://pypi.org/classifiers.

Changes proposed in this merge request:

• setup.py: List useful links using project_urls
• setup.py: Specify minumum python vresion using python_requires
• setup.py: Add project classifiers

This merge request, when approved, will close issue/bug:

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