COMP: Improve arguments for GradientAnisotropicDiffusionImageFilter.

Addresses:

WARNING: In
/home/matt/src/ITK/Modules/Filtering/AnisotropicSmoothing/include/itkAnisotropicDiffusionImageFilter.hxx,
line 82
GradientAnisotropicDiffusionImageFilter (0x12ce520): Anisotropic diffusion
unstable time step: 0.25
Stable time step for this image must be smaller than 0.125

Change-Id: I31d8aae06a14d7be695e1ba8319c72e9c2fed766
Merge "COMP: Improve arguments for GradientAnisotropicDiffusionImageFilter."