hosing experiments subroutines

[mzapponi]

I am including here the two subroutines I setup with the help of Dima and Patrick to add freshwater anomaly around the coasts of Antarctica (with different masks options), at the surface or at specific depths.
I also included a passive tracer where the freshwater anomaly is imposed (tra_304) and it is possible to modify the temperature field to take into account the latent heat of fusion corresponding to the freshwater flux.

In this case I use "linfs" as vertical coordinate so for the surface I modify the virtual salinity flux instead of imposing an actual freshwater volume.

One thing that would make it easier to use would be for sure to add two flags in the config files to call the experiments without having to do it manually and then recompile (but taking into account that part of it is only for linfs), I didn't do it because I had to modify manually the flux amount that was time-dependent so in the end I left it like this.
I hope this is a good start at least for now.

[patrickscholz]

in moment the CI test are failing, i guess this needs more encapsulation so it doesnt mess with our default cases