Storage efficiency notation per any time unit.

[nhoening]

Right now, we have to set storage-efficiency per the time unit of the sensor (how we measure the sensor, e.g. per 15 minutes). But the OEM will usually tell us an efficiency with a different resolution, e.g. per day.

As a follow-up to # 679, we want to support setting a storage efficiency in units of %/, and let the server convert to units of %/. Note that this is a compound interest calculation, which is not supported by pint. *

• For example, a storage efficiency of 99 percent per (absolute) day, for scheduling a 1-hour resolution sensor, should be passed to the scheduler as a storage efficiency of $0.99^{1/24}$.