Merge branch 'develop' of https://git.rwth-aachen.de/ita/ITAPropagationPathSim into psc

.../ITAPropagationPathSim/CombinedModel/DiffractionLocator.h

...de/ITAPropagationPathSim/CombinedModel/ImageConstructor.h

...e/ITAPropagationPathSim/CombinedModel/PropagationEngine.h

...e/ITAPropagationPathSim/CombinedModel/PropagationShapes.h

...TAPropagationPathSim/CombinedModel/DiffractionLocator.cpp

src/ITAPropagationPathSim/CombinedModel/ImageConstructor.cpp

...ITAPropagationPathSim/CombinedModel/PropagationEngine.cpp

tests/CombinedModel/CombinedModelTest.cpp

tests/CombinedModel/GRAS_scene5.cpp

tests/CombinedModel/GRAS_scene6.cpp

tests/CombinedModel/UrbanTrajectory.cpp

tests/CombinedModel/stienen2019auralization_INTERNOISE.cpp