Dev ww3 nest

[bjorkqvi]

WW3 nesting.

• Multiple nests should work, same as SWAN
• Automatically writes spectral output and set up pre- and post-processing
• For some reason the ounf of the nested grid seems to produce a netcdf with 0 values, but when reran by hand with the identical nml-files etc. it produces a correct netcdf. Reason still unknown.