Add Debian packaging tree

This merge request adds a Debian packaging tree to the repository.

To enable the testing to work on Debian, I had to update the tests in test_entrypoint.py so they are skipped if pytest-console-scripts module is not available. This is required as this module is not currently available on Debian.

I have allowed the test on Debian:Buster to fail as python3-coverage>6.4 is not available (required for the sigterm=true in pyproject.toml)