Merge branch 'adaptive_softening' into 'master'

configure.ac

doc/RTD/source/CitingSWIFT/index.rst

doc/RTD/source/HydroSchemes/adaptive_softening.rst

doc/RTD/source/HydroSchemes/index.rst

examples/HydroTests/EvrardCollapse_3D/plotEnergy.py

examples/parameter_example.yml

src/Makefile.am

src/adaptive_softening.h

src/adaptive_softening_iact.h

src/adaptive_softening_struct.h

src/cell_drift.c

src/drift.h

src/engine_maketasks.c

src/gravity/MultiSoftening/gravity.h

src/gravity_properties.c

src/gravity_properties.h

src/hydro/AnarchyPU/hydro_iact.h

src/hydro/AnarchyPU/hydro_part.h

src/hydro/Gadget2/hydro_iact.h

src/hydro/Gadget2/hydro_part.h