Don't load ParticleIDs when using remap_ids

doc/RTD/source/InitialConditions/index.rst

doc/RTD/source/ParameterFiles/parameter_description.rst

examples/main.c

examples/main_fof.c

src/common_io.c

src/common_io.h

src/parallel_io.c

src/parallel_io.h

src/serial_io.c

src/serial_io.h

src/single_io.c

src/single_io.h

src/space.c