small fixes

example/Vector/0_simple/main.cpp

example/Vector/3_molecular_dynamic/Makefile

example/Vector/3_molecular_dynamic/main_vl_sym.cpp

example/Vector/6_complex_usage/Makefile

example/Vector/6_complex_usage/main.cpp

openfpm_data

openfpm_io

openfpm_pdata.doc

script/install_PETSC.sh

src/Vector/vector_dist.hpp

src/Vector/vector_dist_cell_list_tests.hpp

src/Vector/vector_dist_comm.hpp

src/main.cpp