ENH: Update IntensitySegmenter from r11 to r12

ENH: Changed IntensitySegmenter CLI category in Slicer
ENH: The input image is loaded as a float image. This allows to use float ranges.
ENH: Addition of a default voxel value in case the range does not cover this value
ENH: Addition of tests to cover more options

http://www.nitrc.org/plugins/scmsvn/viewcvs.php?root=dentaltools&view=rev
Merge pull request #755 from fbudin69500/update-IntensitySegmenter

ENH: Update IntensitySegmenter from r11 to r12