Reconsider FiberPosition, CobraPosition, and FiducialFiberPosition tables

There's a lot of overlap between these tables, and the naming of fields is confusing. I think that the fiberId is a unique int from FiberPosition (although it's only 4 bytes); what I'm proposing calling FiberPositionSerial in INSTRM-762) which is confusing as elsewhere I think fiberId is used to refer to a cobra – maybe we should use cobraId consistently (and not worry about the fact that they are spots, not cobras, in the engineering mask!). Or maybe I don't understand the point of fiberId as we are not currently moving things; is it intended to be the "ID for a given cobra/fiducial for this visit"? If so, I think we should come up with a better name.

It looks to me as if FiberPosition is the union of the cobra and fiducial position tables for a given visit – is that right? If so, we really need it?

At the very least the column names in all these tables need to be expanded!