Use of FrontEndCfg::toCharge in Star
Follow up on !584 (merged).
FrontEndCfg::toCharge should be used to convert a global DAC value to a charge in electrons.
This is not used in libStar, but now that StarConversionTools exists, it might be possible. Question is whether an individual calibration is needed for each AbcStar, and if so how to map that to an API.