Fixing vector expressions on GPU for slicer []

CMakeLists.txt

src/CMakeLists.txt

src/FiniteDifference/FD_expressions.hpp

src/Operators/Vector/cuda/vector_dist_operators_cuda.cuh

...erators/Vector/tests/vector_dist_operators_tests_util.hpp

src/Operators/Vector/vector_dist_operators.hpp

src/Operators/Vector/vector_dist_operators_unit_tests.cu

src/config/config_cmake.h.in