Proper Exit Codes

[FG-TUM]

Is your feature request related to a problem? Please describe.
Currently when we call Simulation::exit() We either pass -1, 1, or an arbitrary number. The latter is nice to directly grep from the crashing simulation into the code but might become unmaintainable in the long run.

Describe the solution you'd like
One header defining (enum?) constants for each exit state which are then used as an argument for Simulation::exit().

Describe alternatives you've considered

Additional context

$ grep -Erni 'Simulation::exit' src | wc -l
260