#376: Rework import structure in LBAF_app and other files

[tlamonthezie]

Fixes #376

This pull request includes the following related to the rework of the import structure

• Setup lbaf in editable mode (added to the requirements files for pip)
• Make setup working and test :
  • Validation & Corrections for the package setup
  • Addition of a console script (to run the LBAF application directly by typing lbaf in a console)
• Some code quality changes (with the help of Pylint)
• Some development configuration files to help with code quality
• Refactoring
• upgrade acceptance tests and stepper tests to be run also with python 3.9 on the CI
• Update README.md