Merge branch 'master' into multi_softening

src/black_holes/EAGLE/black_holes_part.h

src/black_holes/EAGLE/black_holes_properties.h

src/cell.c

src/collectgroup.c

src/cooling/EAGLE/cooling.c

src/cooling/EAGLE/cooling_rates.h

src/cooling/EAGLE/cooling_tables.c

src/cooling/EAGLE/newton_cooling.c

src/cooling/grackle/cooling.h

src/engine.c

src/engine.h

src/hydro/Gadget2/hydro.h

src/hydro/Gadget2/hydro_part.h

src/hydro/PressureEnergy/hydro.h

src/hydro/PressureEnergy/hydro_iact.h

src/hydro/PressureEnergy/hydro_part.h

src/hydro_properties.c

src/pressure_floor.c

src/pressure_floor.h

src/pressure_floor/GEAR/pressure_floor.h