ENH: GeodesicActiveContourShapePrior deals with DerivativeSigma equal to zero

Similar to 6eb26b3, this commit manages the case that DerivativeSigma is
equal to zero for the GeodesicActiveContourShapePrior filter.

Change-Id: I1ee9ba910578c7ae41cb295ddcb5ee087c1b6e58
DOC: Make comment the Doxygen brief

The prior formatting was incorrect, and didn't not result in correctly
formatted output.

Change-Id: I59abb4948755669c9de76bd91e0a893610bc31f5
Merge topic 'gac-shapeprior-with-zero-derivativesigma'

a46334f9 ENH: GeodesicActiveContourShapePrior deals with DerivativeSigma equal to zero
Merge topic 'FixCannyEdgeDoxygen'

e6908a9b DOC: Make comment the Doxygen brief