Do away with voxel-wise affine Jacobians

[gdevenyi]

These files are huge and have a single value everywhere, can we achieve calculation using a combination of the ANTs tools and bash/awk and ImageMath to add the values.

dbm/intermediate/{affine,delin}

[gdevenyi]

Need to ConvertTransformFile 3 affine.mat affine.mat --convertToAffineType to fix the CompositeTransform generated by the ANTs averager.

[gdevenyi]

Steal awk-based math from https://github.com/CoBrALab/minc-toolkit-extras/blob/master/xfm2det

[gdevenyi]

I implemented it in ANTs, waiting on release.
ANTsX/ANTs#1712