Adding Draw particles functionalities

src/Draw/DrawParticlesGrid.hpp

src/Draw/DrawParticles_unit_tests.hpp

src/Draw/PointIterator.hpp

src/FiniteDifference/mul.hpp

src/Operators/Vector/vector_dist_operator_assign.hpp

src/Operators/Vector/vector_dist_operators_apply_kernel.hpp

.../Vector/vector_dist_operators_apply_kernel_unit_tests.hpp

src/Operators/Vector/vector_dist_operators_extensions.hpp

src/Solvers/umfpack_solver.hpp

src/main.cpp

src/util/util_num.hpp

src/util/util_num_unit_tests.hpp