Corrected metadata for spatially varying bottom friction

[arango]

There is a typo in Data/ROMS/CDL/grd_spherical.cdl. The spatially varying bottom friction arrays are defined at RHO-grid points:

        double rdrag(eta_rho, xi_rho) ;
                rdrag:long_name = "linear bottom drag coefficient" ;
                rdrag:units = "meter second-1 ;
                rdrag:coordinates = "lon_rho lat_rho" ;
        double rdrag2(eta_rho, xi_rho) ;
                rdrag2:long_name = "quadratic bottom drag coefficient" ;
                rdrag2:coordinates = "lon_rho lat_rho" ;
        double ZoBot(eta_rho, xi_rho) ;
                ZoBot:long_name = "time invariant, bottom roughness length" ;
                ZoBot:units = "meter ;
                ZoBot:coordinates = "lon_rho lat_rho" ;

Many thanks to Aijun Zhang for bringing this to my attention.

I also corrected a typo in ad_set_vbc.F for 2D applications. Many thanks to Kate for reporting this problem.