Add additional stats/aseg.VINN.stats file

[dkuegler]

This PR adds a new stats file for the segmentation-based mri/aseg.no_CC.mgz in stats/aseg.VINN.mgz.
This includes the Left/Right-Cerebral-Cortex labels in the table. -- The TotalGray volume (avaliable after surfaces) is still not available (this is in the header with Measures), but depends on the Cortical Gray Matter volumes (which depends on the surface-derived volume). Because of differing conventions on how this is computed, we do not mix this here.

Also renames the statsfile stats/aseg+DKT.mgz computed from mri/aparc.DKTAtlas+aseg.deep.mgz to stats/aseg+DKT.VINN.mgz. stats/aseg+DKT.mgz is generated as a softlink for compatibility (pointing to stats/aseg+DKT.VINN.stats).

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The previous approach is described below.

The problem is that these values cannot be loaded with asegstats2table.

This PR adds "sums" over Cortical GM in Measures as talked about in #676.

• Add CortextVol, lhCortexVol, rhCortexVol, TotalGrayVol as keys for measures
• Add these measures into run_fastsurfer for aseg+DKT.stats

Example of content update of aseg+DKT.stats.

# Measure Mask, MaskVol, Mask Volume, 1747144.000000, mm^3
# Measure BrainSeg, BrainSegVol, Brain Segmentation Volume, 1385005.314630, mm^3
# Measure BrainSegNotVent, BrainSegVolNotVent, Brain Segmentation Volume Without Ventricles, 1313802.684199, mm^3
# Measure SupraTentorial, SupraTentorialVol, Supratentorial volume, 1228319.463260, mm^3
# Measure SupraTentorialNotVent, SupraTentorialVolNotVent, Supratentorial volume, 1157116.832829, mm^3
# Measure SubCortGray, SubCortGrayVol, Subcortical gray matter volume, 66030.583679, mm^3
# Measure rhCortexVol, rhCortexVol, Right hemisphere cortical gray matter volume (segmentation-based), 271607.121787, mm^3
# Measure lhCortexVol, lhCortexVol, Left hemisphere cortical gray matter volume (segmentation-based), 265131.161238, mm^3
# Measure CortexVol, CortexVol, Total cortical gray matter volume (segmentation-based), 536738.283025, mm^3
# Measure TotalGrayVol, TotalGrayVol, Total gray matter volume (all segmentation-based), 728047.728233, mm^3
# Measure rhCerebralWhiteMatter, rhCerebralWhiteMatterVol, Right hemisphere cerebral white matter volume, 277147.639639, mm^3
# Measure lhCerebralWhiteMatter, lhCerebralWhiteMatterVol, Left hemisphere cerebral white matter volume, 277477.805146, mm^3
# Measure CerebralWhiteMatter, CerebralWhiteMatterVol, Total cerebral white matter volume, 554625.444785, mm^3

[dkuegler]

I looked into asegstats2table and the format I have chosen here is not compatible with that script.

There is also no easy way to resolve this ambiguity, three options:

1. use the lhCortex Measure that is usually filled from the surfaces (so it would not be clear that this is volume-based)
2. put a Cortical area line into the table (this would mean the "sum" of all regions might be high, but this property did not hold before either anyways, because the cortex was not in aseg.stats before
3. Generate a second file for aseg.stats -- maybe aseg.deep.stats ?

[dkuegler]

Ready for review. Current state is tested and runs with expected outputs.