ww3_prnc not able to handle curv grid for unst mesh

[mickaelaccensi]

Is your feature request related to a problem? Please describe.
using a forcing field defined on a curvilinear, ww3_prnc runs without success the preprocessing if the model grid is an unstructured mesh

Describe the solution you'd like
need to be implemented

Describe alternatives you've considered
use xesmf to interpole curv grid into rect grid