Convert units

[roaldarbol]

With the ability to store metadata (#19), I think it would make sense to make some functions that convert times (millisecond/second/minute/hour/day) and position (pixel (with calibration factor): mm/ cm/ m/ km).

If we do venture into recording the trace of which operations happened to the dataset, we could also try to re-run that flow whenever a conversion is made... but that sounds like a ton of work!