introduce pre-commit with blake8 and flake checks

.pre-commit-config.yaml

azure-pipelines.yml

build_utils/create_and_pack_executable.py

build_utils/cut_changelog.py

docs/conf.py

package/PartSeg/__init__.py

package/PartSeg/common_gui/error_report.py

package/PartSeg/common_gui/stack_image_view.py

package/PartSeg/segmentation_analysis/image_view.py

package/PartSegCore/analysis/__init__.py

package/tests/test_mso.py

package/tests/test_qt_part/test_sentry.py

requirements/requirements_dev.txt

setup.cfg

setup.py