Merge branch 'master' into parameter_file_in_snapshot

examples/CosmoVolume/cosmoVolume.yml

examples/ExternalPointMass/externalPointMass.yml

examples/SedovBlast/sedov.yml

examples/SodShock/sodShock.yml

examples/UniformBox/uniformBox.yml

examples/main.c

examples/parameter_example.yml

examples/plot_tasks.py

examples/plot_tasks_MPI.py

src/Makefile.am

src/cell.h

src/debug.c

src/drift.h

src/engine.c

src/engine.h

src/hydro/Default/hydro.h

src/hydro/Gadget2/hydro.h

src/hydro/Gadget2/hydro_io.h

src/hydro/Minimal/hydro.h

src/hydro/Minimal/hydro_iact.h