Reading arrays now uses new io_props structure

examples/main.c

src/Makefile.am

src/common_io.c

src/common_io.h

src/gravity/Default/gravity_io.h

src/hydro/Gadget2/hydro_io.h

src/io_properties.h

src/parallel_io.c

src/single_io.c

src/single_io.h