COMP: Test for itkCustomColormapFunction

This test checks the itkCustomColormapFunction class. Reads the
./input/bone.txt file and creates a custom color map based on that input.

This improves code coverage

Change-Id: I1278b7469936939ca0fe652b59d5c6178aa407b3
Merge topic 'CustomcolorMapFunctionTestFix'

1cc091a6 COMP: Test for itkCustomColormapFunction