Merge branch 'logger_api1' into 'master'

configure.ac

examples/main.c

logger/logger_python_wrapper.c

logger/logger_tools.h

src/Makefile.am

src/cell.c

src/engine.c

src/engine_redistribute.c

src/gravity/MultiSoftening/gravity_logger.h

src/gravity_io.h

src/hydro/Gadget2/hydro_logger.h

src/hydro_io.h

src/logger.c

src/logger.h

src/logger_io.h

src/runner_others.c

src/stars/Default/stars_io.h

src/stars/Default/stars_logger.h

src/stars_io.h

tests/testLogger.c