Add epsilon_rho and epsilon_P to hydro properties + formatting

examples/parameter_example.yml

src/const.h

src/hydro/AnarchyPU/hydro_iact.h

src/hydro/Gadget2/hydro_iact.h

src/hydro/Gasoline/hydro_iact.h

src/hydro/Gizmo/hydro_iact.h

src/hydro/Minimal/hydro_iact.h

src/hydro/None/hydro_iact.h

src/hydro/Phantom/hydro_iact.h

src/hydro/Planetary/hydro_iact.h

src/hydro/PressureEnergy/hydro_iact.h

src/hydro/PressureEnergyMorrisMonaghanAV/hydro_iact.h

src/hydro/PressureEntropy/hydro_iact.h

src/hydro/SPHENIX/hydro_iact.h

src/hydro/Shadowswift/hydro.h

src/hydro/Shadowswift/hydro_iact.h

src/hydro/Shadowswift/hydro_iact_boundary.h

src/hydro/Shadowswift/hydro_velocities.h

src/hydro_properties.c

src/hydro_properties.h