Merge branch 'open_source' into develop

# Conflicts:
#	.gitattributes
#	apps/cpu/Applications.cmake
#	apps/cpu/LidDrivenCavity/LidDrivenCavity.cpp
#	cpu.cmake
#	gpu.cmake
#	src/cpu/VirtualFluids.h
#	src/cpu/VirtualFluidsCore/BoundaryConditions/VelocityBCAlgorithm.cpp
#	src/cpu/VirtualFluidsCore/CMakeLists.txt
#	src/cpu/VirtualFluidsCore/Parallel/NullCommunicator.h