Set Fresnel map directly in constructor of IComputationTerm

Core/Computation/IComputationTerm.cpp

Core/Computation/IComputationTerm.h

Core/Computation/MainComputation.cpp

Core/Computation/MainComputation.h

Core/Computation/ParticleLayoutComputation.cpp

Core/Computation/ParticleLayoutComputation.h

Core/Computation/RoughMultiLayerComputation.cpp

Core/Computation/RoughMultiLayerComputation.h

Core/Computation/SpecularComputation.cpp

Core/Computation/SpecularComputation.h