NetCDF coordinates attribute

[arango]

Updated NetCDF output files to report a full coordinates attribute. For example:

        float temp(ocean_time, s_rho, eta_rho, xi_rho) ;
                temp:long_name = "potential temperature" ;
                temp:units = "Celsius" ;
                temp:time = "ocean_time" ;
                temp:coordinates = "lon_rho lat_rho s_rho ocean_time" ;
                temp:field = "temperature, scalar, series" ;

I also corrected climatological clock to start from year 1 instead of 0:

        double ocean_time(ocean_time) ;
                ocean_time:long_name = "averaged time since initialization" ;
                ocean_time:units = "seconds since 0001-01-01 00:00:00" ;