Save layout string in netcdf outputs

• Save the layout string in restart files.

  Aborts attempts to load a restart file with a different layout than the one set in the rest of the code / input file.

• Save layout string in the regular netcdf output

• Always save the grid sizes

It is useful to be able to see which layout was used to produce particular data both for post processing diagnostics and for reproducibilty. It is particularly important for reusing restart files as it is essential that the data in the restart file has the same layout as used in the active simulation reading this in.

Also always saves the grid sizes, primarily for post processing, but could also be used for consistency checks on restart.