STYLE : code factorization in textures

...eatureExtraction/otbAngularSecondMomentumTextureFunctor.h

Code/FeatureExtraction/otbContrastTextureFunctor.h

Code/FeatureExtraction/otbCorrelationTextureFunctor.h

Code/FeatureExtraction/otbDifferenceEntropyTextureFunctor.h

Code/FeatureExtraction/otbEntropyTextureFunctor.h

...tureExtraction/otbInverseDifferenceMomentTextureFunctor.h

Code/FeatureExtraction/otbSumAverageTextureFunctor.h

Code/FeatureExtraction/otbSumEntropyTextureFunctor.h

Code/FeatureExtraction/otbSumVarianceTextureFunctor.h

Code/FeatureExtraction/otbTextureFunctorBase.h

Code/FeatureExtraction/otbVarianceTextureFunctor.h