Add dump functions to remaining engine data

src/cooling.c

src/cooling.h

src/engine.c

src/gravity_properties.c

src/gravity_properties.h

src/hydro_properties.c

src/hydro_properties.h

src/parser.c

src/parser.h

src/physical_constants.c

src/potential.c

src/potential.h

src/restart.c

src/restart.h

src/sourceterms.c

src/sourceterms.h

src/space.c