Move data about execution from the Config class to the Execution class

[Nelly-Barret]

See #86

[Nelly-Barret]

I am even thinking of getting rid of the Config class, because this can be stored in the Execution class and parameters are either:

• given by the user in the cmd line
• set up by the code

So we do not really need a parameter.ini file, and thus the Config class looses its interest.

Therefore, I will try to get rid of the Config class and its associated file parameter.ini, set up parameters and working directory from the code

[Nelly-Barret]

Done through https://github.com/Nelly-Barret/BETTER-fairificator/pull/91