Introduce vtkHDRReader to open Radiance HDR files

IO/Image/CMakeLists.txt

IO/Image/Testing/Cxx/CMakeLists.txt

IO/Image/Testing/Cxx/TestHDRReader.cpp

IO/Image/Testing/Data/Baseline/TestHDRReaderRGBE.png.sha512

IO/Image/Testing/Data/Baseline/TestHDRReaderXYZ.png.sha512

IO/Image/vtk.module

IO/Image/vtkHDRReader.cxx

IO/Image/vtkHDRReader.h

IO/Image/vtkImageReader2Factory.cxx

Testing/Data/gradient_xyz.hdr.sha512

Testing/Data/spiaggia_di_mondello_1k.hdr.sha512