Merge branch 'drop_opencv2_support' into 'develop'

Data/Baseline/OTB-Applications/Files/clDT_ConfMatQB1cv2.dt

.../Baseline/OTB-Applications/Files/clDT_ModelQB1-opencv2.dt

Data/Input/Classification/clDT_ModelQB1-opencv2.dt

Data/Input/Classification/clDT_ModelQB1cv2.dt

Documentation/Cookbook/rst/CompilingOTBFromSource.rst

.../Applications/AppClassification/include/otbTrainBoost.hxx

...ations/AppClassification/include/otbTrainDecisionTree.hxx

Modules/Applications/AppClassification/test/CMakeLists.txt

...LearningBase/include/otbKMeansImageClassificationFilter.h

...s/Learning/LearningBase/include/otbMachineLearningModel.h

...Learning/LearningBase/include/otbMachineLearningModel.hxx

...earning/Supervised/include/otbBoostMachineLearningModel.h

...rning/Supervised/include/otbBoostMachineLearningModel.hxx

.../Supervised/include/otbBoostMachineLearningModelFactory.h

...upervised/include/otbBoostMachineLearningModelFactory.hxx

Modules/Learning/Supervised/include/otbCvRTreesWrapper.h

.../Supervised/include/otbDecisionTreeMachineLearningModel.h

...upervised/include/otbDecisionTreeMachineLearningModel.hxx

...ised/include/otbDecisionTreeMachineLearningModelFactory.h

...ed/include/otbDecisionTreeMachineLearningModelFactory.hxx