Ensure pixels in XY and YZ projections are square

[raacampbell]

We get spherical-looking PSFs when zooming in. That's annoying fix it.

[raacampbell]

You can do, for example, h.hPSF_ZXax.DataAspectRatio=[10,128,1] But this moves the axes about. So a little thought is needed regarding how best to do this. Otherwise we could axes overlapping and all sorts of other horrible stuff.