Add Pylint as a python static code analyzer

[arm4b]

This PR adds Pylint https://pylint.pycqa.org/en/latest/ as a static code analyser for the Python codebase, for quick spotting the common mistakes, errors and enhancing the python coding standards in a minimal automated way.

With #297, closes #271

• Add pylint to the CI pipeline
  • the CI will fail highlighting some existing issues
  • https://github.com/bitovi/bitops/runs/8254149395?check_suite_focus=true#step:7:16
• Update the py code to pass the pylint checks

Quick run:

pip3 install tox
tox -e pylint

[arm4b]

The overall cosmetic pylint refactoring is done and pylint check is now succeeding and is part of the CI.

However, some parts of the codebase will need more structural rework like extracting some huge functions into classes.
We temporary silence them for now to make pylint pass and make dedicated Issues to address them in the future:

• Refactor install_plugins() in install_plugins.py #329
• Refactor deploy_plugins() in deploy_plugins.py #328
• Refactor get_config_list() in utilities.py #327

^^ these would be also good first issues/PRs easier to tackle in between the tasks.