Starting to create indoor diffraction test

src/ITAPropagationPathSim/ConvexDiffraction/EngineImpl.cpp

tests/CMakeLists.txt

tests/ConvexDiffraction/KesselLoudspeakerCabinet.cpp

tests/ConvexDiffraction/KesselLoudspeakerCabinet.json

tests/ImageModel/SimpleImageModelTest.cpp

tests/ImageModel/SimpleUrbanImageModelTest.cpp

tests/IndoorDiffraction/CMakeLists.txt

tests/IndoorDiffraction/SimpleIndoorDiffractionTest.cpp