Added vector iterator

src/Decomposition/CartDecomposition.hpp

src/Grid/grid_dist_id.hpp

src/Grid/grid_dist_id_iterator.hpp

src/Grid/grid_dist_id_unit_test.hpp

src/Grid/grid_dist_key.hpp

src/Space/space.hpp

src/Space/space_key.hpp

src/Vector/vector_dist.hpp

src/Vector/vector_dist_iterator.hpp

src/Vector/vector_dist_key.hpp

src/Vector/vector_dist_unit_test.hpp

src/main.cpp

src/metis_util_unit_test.hpp