Merge branch 'star_formation_birth_struct' into 'master'

src/feedback/EAGLE/feedback.c

src/feedback/GEAR/stellar_evolution.c

src/parallel_io.c

src/serial_io.c

src/single_io.c

src/star_formation/EAGLE/star_formation.h

src/star_formation/EAGLE/star_formation_io.h

src/star_formation/EAGLE/star_formation_struct.h

src/star_formation/GEAR/star_formation.h

src/star_formation/GEAR/star_formation_io.h

src/star_formation/GEAR/star_formation_struct.h

src/star_formation/QLA/star_formation_io.h

src/star_formation/QLA/star_formation_struct.h

src/star_formation/none/star_formation_io.h

src/star_formation/none/star_formation_struct.h

src/stars/Default/stars_part.h

src/stars/EAGLE/stars.h

src/stars/EAGLE/stars_io.h

src/stars/EAGLE/stars_part.h

src/stars/GEAR/stars.h