Use cki_lint.sh

Use cki_lint.sh as the default command to test the project.

This command should be used in all python cki projects, and includes the runs the following commands:

• flake8
• pydocstyle
• isort
• pylint

To pass successfully all this checks, we've done some commits.

Required by infrastructure#41 (closed)

Supersedes !199 (closed)