[vtkusers] smoothing vtkImageData with vtkImageGaussianSmooth

[Liam Kurmos]

> Are you setting gaussianFilter->SetStandardDeviations()
>
I reduced with gaussianFilter->SetStandardDeviations(1,1,1) as the
default (2,2,2) seemed to have an excessive effect vs. what i imaged 2
pixels would give (going by the max field value).

I would have to visualise some slices of the field and make sure i
know exactly how gaussian convolution smoothing works before i could
say there was a problem with it though.

Liam