BUG: 2632. GrowCut crashes with input volume of type char.

The intensity image is assigned to the first input on the
vtkITKGrowCutImageFilter which forces the output segmentation
image to have the same pixel type. But the output segmetentation
is assumed at the ITK level to be same pixel type as the gesture
image.

Overrode ExecuteInformation() so information from the second
input is propagated to the output image, so the gesture image
and output segmentation image have the same pixel type.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21170 3bd1e089-480b-0410-8dfb-8563597acbee