Support pre-commit checks used in AdaCore/e3-core
These are a good example of best style practices for python projects. Adding the associated badges to the README (even though it needs to be rewritten) so the commit is complete and consistent.
Documentation of how to set up and run the checks is in CONTRIBUTING.md
Master `anod` script that dispatches to subscripts for action.
Add `paths` module, which group common path-related constants.
Improve anod-devel-setup to use e3 and logging.
