Remove unused IFresnelMap classes and other unused functions

Core/Computation/IComputationUtils.cpp

Core/Computation/IComputationUtils.h

Core/Computation/ProcessedSample.cpp

Core/Computation/ProcessedSample.h

Core/Computation/SpecularComputation.cpp

Core/Computation/SpecularComputation.h

Core/Computation/SpecularComputationTerm.cpp

Core/Computation/SpecularComputationTerm.h

Core/Multilayer/IFresnelMap.cpp

Core/Multilayer/IFresnelMap.h

Core/Multilayer/IMultiLayerFresnelMap.cpp

Core/Multilayer/IMultiLayerFresnelMap.h

Core/Multilayer/KzComputation.cpp

Core/Multilayer/KzComputation.h

Core/Multilayer/MatrixMLFresnelMap.cpp

Core/Multilayer/MatrixMLFresnelMap.h

Core/Multilayer/ScalarFresnelMap.h

Core/Multilayer/ScalarMLFresnelMap.cpp

Core/Multilayer/ScalarMLFresnelMap.h

Core/Multilayer/SpecularMagnetic.cpp