Improve simu_MCS with the addition of surface fields

[abierjon]

For now, the program LMDZ.MARS/util/simu_MCS.F90 only handles 4D variables from the GCM, with their 4D reference variables in MCS file.

One could add surface (lon,lat,time) variables from the GCM too, as well as their corresponding surface variables in MCS file (coldust, colwice,...) that are needed as references for the interpolation & binning of the GCM variables.