Add feature to store data from cyclic buffer back in time

[robertjensen]

Sometimes a logger can be in a state we it would be advantageous to store data prior to the event in question.

We need a cycling buffer and a way to retrospectively store this data in case of certain events.

[KennethNielsen]

What kind of events do you have in mind?

[robertjensen]

The canonical example would be an ion gauge with a logging criterion of eg ~10%/600s. After 550 seconds the pressure suddenly increases a factor of 10.000. In this case it would be favorable to be able to retrospectively keep the data from the past 550 seconds to be able to tell the detailed development up to the increase.