Merge pull request 'Merge develop with got a merge from open source  before.' (#29) from peters/VirtualFluids_dev:develop 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

Merge pull request 'feature/update_dev_to_os' (#28) from peters/VirtualFluids_dev:feature/update_dev_to_os into open_source

Merge pull request 'feature/update_cpu_to_open_source' (#27) from peters/VirtualFluids_dev:feature/update_cpu_to_open_source into develop

Merge pull request 'feature/enable_gpu_numerical_tests' (#26) from peters/VirtualFluids_dev:feature/enable_gpu_numerical_tests into develop

Merge pull request 'MemoryUtil can determine total physical memory on macOS' (#25) from marcus/VirtualFluids_dev:feature/memoryutil-macos into develop

Merge pull request 'feature/extends_readme' (#10) from peters/VirtualFluids_dev:feature/extends_readme into develop

Merge pull request 'Adds a new constructor to SetKernelBlockVisitor with num processes' (#24) from marcus/VirtualFluids_dev:develop into develop

visit method throws exception if required memory determined from simulation grid exceeds available physical memory

Merge pull request 'Adapt cmake and muparser to dev version,' (#23) from peters/VirtualFluids_dev:open_source into open_source

Merge pull request 'CMake Clean Up.' (#22) from peters/VirtualFluids_dev:feature/adapt_to_open_source into develop

Update cmake to dev version.

Remove VirtualFluidsDefinitions.h header file.
Remove redundant compiler definitions from gpu.cmake.

Few refactorings in cmake. Remove the old openmp flag. Put the intel and gcc libraries in the compiler file.

Make use of the new cmake command: target_link_options, target_compile_options and target_compile_definitions.

Removed unused machine config files.
Removed CAB_COMPILER variable. compiler flag files is now loaded regarding the CMAKE_CXX_COMPILER_ID variable:
	https://cmake.org/cmake/help/latest/variable/CMAKE_LANG_COMPILER_ID.html
Removed the 64 bit support.