Made changes to Hydrostatic halo scripts and included a README file

examples/CoolingHalo/run.sh

examples/HydrostaticHalo/README

examples/HydrostaticHalo/density_profile.py

examples/HydrostaticHalo/hydrostatic.yml

examples/HydrostaticHalo/internal_energy_profile.py

examples/HydrostaticHalo/run.sh

examples/HydrostaticHalo/test_energy_conservation.py

examples/HydrostaticHalo/velocity_profile.py

src/const.h

src/potential/disc_patch/potential.h

src/potential/none/potential.h

src/potential/point_mass/potential.h

src/potential/softened_isothermal/potential.h