Automatic detection of checkpoint placement based on time passed between checkpoints

[RockinRoel]

Currently, the positions of checkpoints are measured before the run, so that they can be displayed in the correct position in the UI. It should however be possible to measure how much time it takes between checkpoints to then infer during the event where the checkpoints are placed.

[bertvandepoel]

Probably we want to offer two options (ideally not through config.json but through the UI): exact measurements or the suggested option here where the position and distance of the checkpoints is extrapolated from the data.