Sink formation

...es/IsolatedGalaxy/IsolatedGalaxy_sink/isolated_galaxy.yml

examples/IsolatedGalaxy/IsolatedGalaxy_sink/makeIC.py

examples/IsolatedGalaxy/IsolatedGalaxy_sink/run.sh

examples/main.c

src/cell.c

src/cell.h

src/drift.h

src/engine.c

src/engine_maketasks.c

src/engine_marktasks.c

src/engine_unskip.c

src/random.h

src/runner.h

src/runner_main.c

src/runner_others.c

src/scheduler.c

src/single_io.c

src/sink/Default/sink.h

src/space.c

src/space.h