Merge branch 'master' into FOF

Makefile.am

configure.ac

doc/RTD/source/ParameterFiles/index.rst

doc/RTD/source/VELOCIraptorInterface/output.rst

examples/KelvinHelmholtz_2D/makeMovie.py

examples/Makefile.am

examples/SodShock_1D/plotSolution.py

examples/parameter_example.yml

examples/plot_gravity_checks.py

examples/plot_scaling_results.py

examples/plot_scaling_results_breakdown.py

src/cell.c

src/cell.h

src/common_io.c

src/cycle.h

src/debug.c

src/engine.c

src/engine_maketasks.c

src/engine_marktasks.c

src/hydro.h