Rename enum CorrectType entries

This MR improves nomenclature in the JonesParameters class somewhat.

I think these may originally have corresponded to names stored in 'parmdb' files, but imho they're confusing. Particular when I see 'gain', 'phase' or 'amplitude' I think of resp. "scalar complex", "scalar phase" and "scalar amplitude", not diagonal solutions, which is what they used to mean. These names also match with the 'CalType' enum in Dp3.

CorrectType also doesn't read well, I read it as the opposite of an "IncorrectTye". CorrectionType would fix that, but imho GainType is a bit closer to what it actually is. A solved gain can also be stored/written in this class, but that's not necessarily a "correction" at that point.