fix: global calculation to user-defined values
fix: spm_smooth requires FWHM in mm (not voxels)
test: add file number to file selection
SnPM13 sub-version updated to SnPM13.06
Revert "fix: spm_smooth requires FWHM in mm (not voxels)"

This reverts commit 409ec14f4b1ba63603d6e0250c411f7320799c5c.
Comment on FWHM units for spm_smooth
test: fix spm results should compare with batch results
test: prop and absolute thresholding and masking