Added more tests

apps/benchmarks/CMakeLists.txt

apps/benchmarks/CommunicationGPU/CMakeLists.txt

apps/benchmarks/CommunicationGPU/CommunicationGPU.cpp

apps/benchmarks/CommunicationGPU/CommunicationGPU.py

apps/benchmarks/CommunicationGPU/CommunicationGPUCodeGen.py

apps/benchmarks/CommunicationGPU/GPUPackPerformance.cpp

apps/benchmarks/CommunicationGPU/GPUPackPerformance.py

python/lbmpy_walberla/storage_specification.py

src/core/mpi/BufferSystemHelper.impl.h

src/gpu/communication/MemcpyPackInfo.h

src/gpu/communication/MemcpyPackInfo.impl.h

src/gpu/communication/UniformGPUScheme.h

src/gpu/communication/UniformGPUScheme.impl.h