Merge branch 'logger_add_modules' into 'master'

configure.ac

src/Makefile.am

src/chemistry/GEAR/chemistry_logger.c

src/chemistry/GEAR/chemistry_logger.h

src/chemistry/none/chemistry_logger.c

src/chemistry/none/chemistry_logger.h

src/chemistry_logger.h

src/engine.c

src/feedback/GEAR/feedback.c

src/gravity/MultiSoftening/gravity_logger.c

src/gravity/MultiSoftening/gravity_logger.h

src/hydro/Gadget2/hydro_logger.c

src/hydro/Gadget2/hydro_logger.h

src/hydro/SPHENIX/hydro_logger.c

src/hydro/SPHENIX/hydro_logger.h

src/logger.c

src/logger.h

src/logger_history.c

src/logger_history.h

src/star_formation/GEAR/star_formation_particle_logger.c