Runs a uniform cosmological box with imposed abundances for a set of
elements entering the Grackle cooling. 
The simulation is run  with the Grackle thermochemistry, down to redhift 0
where the resulting abundances are compared with predictions.

To run, configure swift with:
  ./configure --with-cooling=grackle_3 --with-grackle=$GRACKLE_ROOT


Note : the script getPrimordialAbundances.py helps in the setting of the
initial abundances.
