Moved unit-tests into tests/unit-tests

CMake/VirtualFluidsMacros.cmake

docs/pages/Regression-Tests.md

src/basics/CMakeLists.txt

src/cpu/core/CMakeLists.txt

src/gpu/GridGenerator/CMakeLists.txt

src/gpu/core/CMakeLists.txt

src/lbm/CMakeLists.txt

tests/unit-tests/basics/CMakeLists.txt

tests/unit-tests/basics/StringUtilities/StringUtilTest.cpp

tests/unit-tests/basics/config/ConfigurationFileTest.cpp

tests/unit-tests/basics/utilities/UbFileInputASCIITest.cfg

tests/unit-tests/basics/utilities/UbFileInputASCIITest.cpp

tests/unit-tests/basics/utilities/Vector3DTest.cpp

tests/unit-tests/cpu/core/CMakeLists.txt

...s/cpu/core/Connectors/FineToCoarseVectorConnectorTest.cpp

tests/unit-tests/gpu/GridGenerator/CMakeLists.txt

...it-tests/gpu/GridGenerator/geometries/BoundingBoxTest.cpp

.../unit-tests/gpu/GridGenerator/geometries/CylinderTest.cpp

...sts/gpu/GridGenerator/geometries/VerticalCylinderTest.cpp

tests/unit-tests/gpu/GridGenerator/grid/DistributionTest.cpp