Added operators on GPU

CMakeLists.txt

src/CMakeLists.txt

src/FiniteDifference/eq_unit_test.cpp

src/FiniteDifference/eq_unit_test_3d.cpp

src/Operators/Vector/vector_dist_operators.hpp

src/Operators/Vector/vector_dist_operators_apply_kernel.hpp

.../Vector/vector_dist_operators_apply_kernel_unit_tests.cpp

...s/Vector/vector_dist_operators_apply_kernel_unit_tests.cu

.../Vector/vector_dist_operators_apply_kernel_unit_tests.hpp

src/Operators/Vector/vector_dist_operators_functions.hpp

src/Operators/Vector/vector_dist_operators_unit_tests.cpp

src/Operators/Vector/vector_dist_operators_unit_tests.cu

src/Solvers/umfpack_solver.hpp

src/unit_test_init_cleanup.hpp