Merge remote-tracking branch 'origin/revert_shark' into release-6.6

...cations/AppClassification/app/otbKMeansClassification.cxx

...nsionalityReductionLearning/include/otbAutoencoderModel.h

...ionalityReductionLearning/include/otbAutoencoderModel.txx

...g/DimensionalityReductionLearning/include/otbPCAModel.txx

Modules/Learning/LearningBase/otb-module.cmake

Modules/Learning/LearningBase/test/CMakeLists.txt

.../Learning/LearningBase/test/otbLearningBaseTestDriver.cxx

Modules/Learning/LearningBase/test/otbSharkUtilsTests.cxx

...vised/include/otbSharkRandomForestsMachineLearningModel.h

...sed/include/otbSharkRandomForestsMachineLearningModel.txx

...supervised/include/otbSharkKMeansMachineLearningModel.txx

Modules/ThirdParty/Shark/include/otbSharkUtils.h

SuperBuild/CMake/External_shark.cmake

SuperBuild/patches/SHARK/shark-2-ext-num-literals-all.diff

SuperBuild/patches/SHARK/shark-2-find-boost-all.diff