Implemented parameter scanning

This is a major commit with quite deep-reaching changes in the code
base. It enables the user to specify multiple values for a model
parameter, which will then be combined into a full-factorial
simulation experiment. Everything seems to work as intended, although
some refactoring would be good, and we still need to add parallelisation
for issue #42.

And yes, I coded all of this between 23:30 and 03:00 on a Saturday
night 😅 🙈