Merge branch 'develop' into feature/united_code

# Conflicts:
#	CMake/VirtualFluidsMacros.cmake
#	CMakeLists.txt
#	src/cpu/VirtualFluidsCore/CoProcessors/MPIIOMigrationBECoProcessor.cpp
#	src/cpu/VirtualFluidsCore/CoProcessors/MPIIOMigrationCoProcessor.cpp
#	src/cpu/VirtualFluidsCore/CoProcessors/MPIIORestartCoProcessor.cpp
#	src/gpu/VirtualFluids_GPU/CMakeLists.txt
#	src/gpu/VirtualFluids_GPU/LBM/Simulation.cpp