[RTM] FIX: Reduce interpolation artifacts in ConformSeries

[effigies]

This PR attempts to make the conformation step minimally disruptive.

• Rescaling and resizing operations are logically separated in calculating the target affine
• Rescaling is only applied if there is a > 0.05mm difference between the original and target zooms
• Resizing is restricted to an integer shift, rather than scaling the intercept; this should avoid half-voxel interpolations if an odd number of voxels are tacked on
• The original image header is copied to the target, reducing the divergence of the header only to changes induced by an updated affine

Additionally, symlinks are disallowed for untouched files, so that the working directory can be created by a docker image and inspected outside.

Fixes #562.

[chrisgorgo]

I assume you have tested that this indeed fixes #562. Correct?

[effigies]

I ran through autorecon1 on sub-07 with no issues, and orig.mgz now looks more reasonable. Running sub-09 now...

[effigies]

sub-09 is working, as well. I did screw up sub-02, however. I think it's the shift that went wrong.

[effigies]

Okay, I believe I've fixed it, but I'm going to need to rerun tests for each subject to verify...

[effigies]

Tested on ds114 sub-02, sub-07 and sub-09. This is good to go.