POLREF: GMW magnet: investigate and gather requirements for calibrations taking into account hysteresis

## Where?

As an insrument scientist on POLREF, I would like a way of calibrating the GMW magnet (controlled by danfysik power supply) which takes hysteresis into account - i.e. the calibration is different depending on the *previous* field(s). [Note: the hysteresis on this GMW magnet is only reproducible when changing from max field - either positive or negative - to the new field - changing from arbitrary field to arbitrary field is not reproducible as you are then on the virgin magnetistation curve].

This ticket is to investigate, in conjunction with scientists:
- What are the exact requirements from a science perspective
- How can we conceptually implement this in IBEX
- What are the limitations of the proposed approach

Once we have answered the above questions, a separate ticket should be created for the actual implementation.

## How?

POLREF scientists asked about this.

## How to Test
_verbose instructions for reviewer to test changes
(**Add before making a PR**)_