Improved documentation + examples code

CHANGELOG.md

example/Numerics/Vortex_in_cell/main_vic_petsc.cpp

example/Vector/0_simple/main.cpp

example/Vector/1_HDF5_save_load/main.cpp

example/Vector/1_celllist/main.cpp

example/Vector/3_molecular_dynamic/main.cpp

example/Vector/5_molecular_dynamic_sym_crs/main.cpp

openfpm_numerics

src/Decomposition/ie_ghost.hpp

src/Grid/grid_dist_id.hpp

src/Grid/staggered_dist_grid_copy.hpp

src/Vector/vector_dist.hpp

src/gargabe.hpp