Pick a consistent basis transformation

[evanberkowitz]

Currently, the convention for basis transformations is inconsistent.

In onePointFunctions it's vector --> U vector but in singleParticleCorrelator and spinSpinCorrelator it's matrix --> U† matrix U. This causes lots of very annoying problem.

We should harmonize, unifying on matrix --> U matrix U†.

[jl-wynen]

SpinSpinCorrelator.computeDerivedCorrelators and OnePointFunctions.computeDerivedCorrelators need to be changed as well.

[jl-wynen]

This whole thing is making it very hard to properly handle correlators. We should just remove transforms from the measurements and store correlators in position space.

[evanberkowitz]

I agree.

If, at some point, we want to do direct calculations at a particular momentum mode (or group irrep, or whatever), we can. But as long as we're doing all-to-all and doing analysis after, we should stick to space.

[evanberkowitz]

Another benefit is that it reduces the number of matrix multiplies in the measurements themselves. They can be done on bootstrap-averaged samples, which is a LOT less, and is done off-line.