.csv output

[j-atkins]

It would be good to add (back) .csv output for CTDs, and potentially other instruments. This would better represent real-life output and potentially mean VirtualShip output could be used by people with less technical backgrounds.

[j-atkins]

Will become more straightforward following #2583, i.e. Parquet file writing in Parcels. Therefore, this issue is best addressed after migrating VirtualShip to Parcels v4 (#218).