Make __version__ global available for all supported python versions

Extract the version information from the packaging and set it as version global. For the still supported python 3.7 this also handles the installation of the importlib-metadata package.

This name must match the setup.cfg name, unfortunately there is no easy / non-ugly way to extract this automatically so no single source of truth.

Here is the 'ugly' way: https://stackoverflow.com/a/60351412

approved this merge request

mentioned in commit 057e7a1b

merged

mentioned in issue #2 (closed)