Flexible paths and patch_up fix

1. The path for the .celsius.yml file is flexible, i.e. searched in a list of possible locations. We also switch to pathlib to build paths to the various files which allow easier expression of the paths.
2. The civ2 failure was due to incorrect values of m and n (patch1 did output a warning about having too many points per patch). Ultimately, this leads to the rd_grille2 interpolation step in civ2 to fail. Such failure is dealt with in the Fortran code by stopping the process, so the python kernel exits.