Switch to function call overload of IComputationTerm and remove obsolete code

Core/Computation/DWBAComputation.cpp

Core/Computation/GISASSpecularComputationTerm.cpp

Core/Computation/GISASSpecularComputationTerm.h

Core/Computation/IComputationTerm.h

Core/Computation/ParticleLayoutComputation.cpp

Core/Computation/ParticleLayoutComputation.h

Core/Computation/RoughMultiLayerComputation.cpp

Core/Computation/RoughMultiLayerComputation.h