#135, #162: Introduce mypy, pylint, isort, gitlab-ci pre-commit hooks

• Add mypy pre-commit hook
• Introduce isort pre-commit hook
• Sort imports in every files
• Fix cyclic import issue in ascii_armor
• Add isort job
• Introduce gitlab-ci-linter pre-commit hook
• Move pylint rules from the Makefile to the pyproject.toml
• Introduce pylint pre-commit hook
• Change pre-commit hooks documentation
• Run lint job with pylint from the image
• Run checks by calling directly the tools without the makefile

Close #135 (closed), #162 (closed).