Floating scalar type mask causes runtime error

[fedorov]

This issue was identified by a Slicer user. I see cast is done in some places already, but I am not sure what is the one place where it should be done to avoid redundancy. Ideally, it should be done only once. @JoostJM do you have a good idea where this should be fixed once and forever?

Traceback (most recent call last):
  File "/Applications/Slicer.app/Contents/Extensions-27399/SlicerRadiomics/lib/python2.7/site-packages/radiomics/scripts/segment.py", line 38, in extractSegment
    feature_vector.update(extractor.execute(imageFilepath, maskFilepath, label))
  File "/Applications/Slicer.app/Contents/Extensions-27399/SlicerRadiomics/lib/python2.7/site-packages/radiomics/featureextractor.py", line 387, in execute
    image, mask = self.loadImage(imageFilepath, maskFilepath)
  File "/Applications/Slicer.app/Contents/Extensions-27399/SlicerRadiomics/lib/python2.7/site-packages/radiomics/featureextractor.py", line 492, in loadImage
    self.generalInfo.addMaskElements(image, mask, self.settings.get('label', 1))
  File "/Applications/Slicer.app/Contents/Extensions-27399/SlicerRadiomics/lib/python2.7/site-packages/radiomics/generalinfo.py", line 107, in addMaskElements
    lssif.Execute(mask)
  File "/Applications/Slicer.app/Contents/lib/Python/lib/python2.7/site-packages/SimpleITK/SimpleITK.py", line 43062, in Execute
    return _SimpleITK.LabelShapeStatisticsImageFilter_Execute(self, *args)
RuntimeError: Exception thrown in SimpleITK LabelShapeStatisticsImageFilter_Execute: /Volumes/Dashboards/Preview/Slicer-0-build/SimpleITK/Code/Common/include/sitkMemberFunctionFactory.hxx:196:
sitk::ERROR: Pixel type: 64-bit float is not supported in 3D byN3itk6simple31LabelShapeStatisticsImageFilterE