ENH : texture formalas correction + add sum entropy

Code/FeatureExtraction/otbContrastTextureFunctor.h

Code/FeatureExtraction/otbDifferenceEntropyTextureFunctor.h

Code/FeatureExtraction/otbSumAverageTextureFunctor.h

Code/FeatureExtraction/otbSumEntropyTextureFunctor.h

Testing/Code/FeatureExtraction/CMakeLists.txt

Testing/Code/FeatureExtraction/otbTextureFunctor.cxx

Testing/Code/FeatureExtraction/otbTextureImageFunction.cxx