DefField.deformationType and detectDeformationType. Also fix applyDeformation
where not using altref

passed. Used by fsl_convert_x5

transformation (e.g. FLIRT registration) during the resampling. Missed imports
in deprecated fsl.utils.transform

complete?

nonlinear.DeformationField

is no longer assumed to be aligned with the reference in voxels - it is
only assumed to be aligned to the reference in world coordinates.

coefficient fields

can get away with it. Can't be bothered figuring out how to adjust srcToRefMat
in convertDisplacementSpace, so am just not supporting it