Fix csv columns order for simulation output
According to the documentation, the simulation results are formatted as csv files (see https://batsim.readthedocs.io/en/latest/output-schedule.html and https://batsim.readthedocs.io/en/latest/output-jobs.html). There is however no guaranty the order of the columns and their types will not change.
It would make parsing results more robust if Batsim guaranty such properties for the output format.
This mainly requires documenting the order of columns and how it may evolve; and writing some tests to avoid any unintentional regressions.