Rework external events
Rework the external Event code and permits users to input generic events that are forwarded to the scheduler without having to code everything in Batsim.
- Descriptive and short
- Use hyphens to separate words
- Only dedicated to the problem.
- Based on Batsim's official master branch.
- Straightforward. Just a sequence of commits. Does not contain merge commits.
- Test results are not worse than before.