Merge branch 'master' into gizmo_fix

README

configure.ac

examples/main.c

examples/parameter_example.yml

src/Makefile.am

src/cell.c

src/cell.h

src/const.h

src/engine.c

src/gravity.c

src/gravity.h

src/gravity/Default/gravity.h

src/gravity/Default/gravity_part.h

src/hydro_properties.c

src/hydro_properties.h

src/multipole.h

src/part.c

src/potential/point_mass/potential.h

src/runner.c

src/runner_doiact_grav.h