Merge branch 'feature/clean_3rd_cmake_macros' into develop

* feature/clean_3rd_cmake_macros:
  Add 3rd library cmake functions.
  Fix gpu cell type.
  Add public include directories.
  CMake: rename the directory variables in a consistent way.
  Remove redundant PointerDefinition file. Make the cmake project more flexible while removing the CMAKE_SOURCE_DIR usage.
  Remove all old unused cmake files.
  Update gitignore file.
  Fix cell type to unsigned int. Adapt basics CMakeLists according to develop.
  Adapt open_source basics to develop.
  Remove unnecessary files in basics.

# Conflicts:
#	CMake/VirtualFluidsMacros.cmake
#	CMakeLists.txt
#	apps/cpu/LidDrivenCavityCPU/CMakeLists.txt
#	apps/gpu/LidDrivenCavity/CMakeLists.txt
#	apps/gpu/LidDrivenCavity/LidDrivenCavity.cpp
#	cpu.cmake
#	gpu.cmake
#	src/basics/CMakeLists.txt
#	src/cpu/VirtualFluidsCore/CMakeLists.txt
#	src/cpu/VirtualFluidsCore/CoProcessors/WriteBoundaryConditionsCoProcessor.cpp
#	src/cpu/VirtualFluidsCore/CoProcessors/WriteBoundaryConditionsCoProcessor.h
#	src/cpu/VirtualFluidsCore/CoProcessors/WriteMacroscopicQuantitiesCoProcessor.cpp
#	src/cpu/VirtualFluidsCore/CoProcessors/WriteMacroscopicQuantitiesCoProcessor.h
#	src/gpu/GksGpu/CMakeLists.txt
#	src/gpu/GksMeshAdapter/CMakeLists.txt
#	src/gpu/GridGenerator/CMakeLists.txt
#	src/gpu/VirtualFluids_GPU/CMakeLists.txt
#	src/gpu/VirtualFluids_GPU/LBM/Simulation.h
#	src/gpu/VirtualFluids_GPU/Output/FileWriter.cpp
#	src/gpu/VirtualFluids_GPU/Parameter/Parameter.h