SimpleITK update causes z-axis orientation bug for some scans

[jpeoples]

There is a bug in SimpleITK that makes some of our data load upside down - in particular between

2.2 and 2.4 versions, there is a switch

(more info on fixing this in slicer here) Slicer/Slicer#7987

Essentially something to do with negative "SpacingBetweenSlices" values, which Aim2 has a lot of!

I found this while working on the GE noise map code. I'm "fixing" by using SimpleITK 2.2.1 for now, but will need to properly fix this at some point probably!