Merge branch 'sampling_multi_image' into develop

Modules/Applications/AppClassification/app/CMakeLists.txt

...tions/AppClassification/app/otbMultiImageSamplingRate.cxx

...Applications/AppClassification/app/otbSampleSelection.cxx

...ations/AppClassification/app/otbTrainVectorClassifier.cxx

Modules/Applications/AppClassification/test/CMakeLists.txt

Modules/Filtering/Statistics/src/otbSamplerBase.cxx

...les/Learning/Sampling/include/otbSamplingRateCalculator.h

...Learning/Sampling/include/otbSamplingRateCalculatorList.h

Modules/Learning/Sampling/src/CMakeLists.txt

Modules/Learning/Sampling/src/otbSamplingRateCalculator.cxx

...s/Learning/Sampling/src/otbSamplingRateCalculatorList.cxx

Modules/Learning/Sampling/test/CMakeLists.txt

...rning/Sampling/test/otbSamplingRateCalculatorListTest.cxx

Modules/Learning/Sampling/test/otbSamplingTestDriver.cxx