DOC: add texture group for doxygen

...eatureExtraction/otbAngularSecondMomentumTextureFunctor.h

Code/FeatureExtraction/otbClusterProminenceTextureFunctor.h

Code/FeatureExtraction/otbClusterShadeTextureFunctor.h

Code/FeatureExtraction/otbContrastTextureFunctor.h

Code/FeatureExtraction/otbCorrelationTextureFunctor.h

Code/FeatureExtraction/otbDifferenceEntropyTextureFunctor.h

Code/FeatureExtraction/otbDifferenceVarianceTextureFunctor.h

Code/FeatureExtraction/otbEnergyTextureFunctor.h

Code/FeatureExtraction/otbEntropyTextureFunctor.h

...ction/otbInformationMeasureOfCorrelation1TextureFunctor.h

...ction/otbInformationMeasureOfCorrelation2TextureFunctor.h

...tureExtraction/otbInverseDifferenceMomentTextureFunctor.h

Code/FeatureExtraction/otbMeanTextureFunctor.h

Code/FeatureExtraction/otbPanTexTextureFunctor.h

Code/FeatureExtraction/otbPanTexTextureImageFilter.h

Code/FeatureExtraction/otbPanTexTextureImageFunctionFilter.h

Code/FeatureExtraction/otbSFSTexturesFunctor.h

Code/FeatureExtraction/otbSFSTexturesImageFilter.h

Code/FeatureExtraction/otbSumAverageTextureFunctor.h

Code/FeatureExtraction/otbSumEntropyTextureFunctor.h