Rich{1,2}: Move RefractivityScaleFactor to own condition

For real data, the refactive index scale factors will get regular (run by run) automatic updates from the pit. As such these conditions really need to be own their own, which is what this MR does. I also introduce the framework to add them with IOVs in the future.

@clemenci can you please check my changes here are correct ?

Also (@gcorti @seaso), am I correct that the master branch is where we should commit things for real data conditions, and the simulation branch is then for MC ? If so then this branch should be cherry-picked to the simulation branch as well, just to make the structure the same between the two, but going forward these conditions will probably not need updating in this branch as scale factors of 1.0 are correct for MC.