Implement --shape-update-method

[gdevenyi]

Add choices for shape update method.

1. ants, average transforms and apply scaled pseudo-inverse to intensity average
2. none perform no shape update, forward-only registration
3. fonov aka OMM-1 method, average forward transforms, invert, apply forward-transform composed with average inverse before intensity average step

https://www.biorxiv.org/content/10.1101/2023.11.30.569378v1.full.pdf