Rename table getters and setters for fluxes as per RFC-322

RFC-322 has us renaming flux fields in tables, e.g. *Flux_flux to *Flux_instFlux for fluxes in counts, and then adding *Flux_flux to mean physical flux (e.g. in Jy).

However, source tables also have getters and setters for instrument flux, such as getPsfFlux. At present (before implementing RFC-322) there is an obvious mapping between field names in source tables and the accessor names, e.g. getPsfFlux returns field psfFlux_flux. If we implement RFC-322 without also renaming the getters and setters then that linkage is broken. For example getPsfFlux will return data from psfFlux_instFlux instead of psfFlux_flux. I fear users will find that confusing and upsetting.

Thus I propose that as we implement RFC-322 we also rename the getters and setters: get/set*Flux becomes get/set*InstFlux, for example getPsfFlux becomes. getPsfInstFlux.

I further propose that we do not add getters and setters for physical flux. By not defining them we reduce the danger that old code will read the wrong thing from source tables: getPsfFlux will simply not exist, instead of returning the wrong thing. (We may decide to add them later, if we really miss them, but that decision is out of scope for this RFC.)

I have taken the liberty of adding as watchers those who weighed in on RFC-322