Merge branch 'split_stars' into 'master'

examples/DwarfGalaxy/README

examples/DwarfGalaxy/dwarf_galaxy.yml

examples/DwarfGalaxy/getIC.sh

examples/DwarfGalaxy/run.sh

examples/ZoomIn/README

examples/ZoomIn/getIC.sh

examples/ZoomIn/run.sh

examples/ZoomIn/zoom_in.yml

examples/plot_task_level.py

examples/plot_tasks.py

src/cell.c

src/cell.h

src/drift.h

src/engine.c

src/map.c

src/map.h

src/runner.c

src/runner_doiact_stars.h

src/scheduler.c

src/scheduler.h