Clean up & add unit tests

Developing a set of python unit tests to have a good coverage of all the DaVinci configuration scripts. As natural consequence, a clean up of the codes is also performed removing typos and simplifying the code when needed.

Addresses: https://gitlab.cern.ch/lhcb-dpa/project/-/issues/179, https://gitlab.cern.ch/lhcb-dpa/project/-/issues/180