Still need to deal with conflicts, I will assign this merge request when the code will be ready.
Basically, I have updated the code done by @yvesrevaz and checked it.
After this merge request, I am planning to improve the code (not a big fan of having a cooling_wrapper file), pass from grackle v2 to v3 and change the way grackle compute the cooling rate (currently only reading a table, in the future it would be possible to compute the chemical network on the fly).