Merge remote-tracking branch 'origin/master' into cell_flags

doc/RTD/source/ParameterFiles/parameter_description.rst

doc/RTD/source/Task/index.rst

examples/HydroTests/SodShock_3D/sodShock.yml

...olatedGalaxy/IsolatedGalaxy_starformation/plotSolution.py

examples/SubgridTests/StellarEvolution/makeIC.py

examples/main.c

examples/parameter_example.yml

src/cell.c

src/cell.h

src/debug.c

src/engine.c

src/engine.h

src/engine_maketasks.c

src/equation_of_state/planetary/tillotson.h

src/feedback/EAGLE/feedback.c

src/feedback/EAGLE/feedback.h

src/feedback/EAGLE/feedback_iact.h

src/feedback/EAGLE/imf.h

src/feedback/none/feedback.h

src/memuse.h