vvl not running in pure zco

[rblod]

zco option (ln_zco) isn't compatible with vvl due to missing initialization of scales factors (only the substitute are initialized in zgr_zco).
Fix: initialize scale factos rather than substitute in zgr_zco:

      DO jk = 1, jpk
         gdept(:,:,jk) = gdept_0(jk)
         gdepw(:,:,jk) = gdepw_0(jk)
         gdep3w(:,:,jk) = gdepw_0(jk)
         e3t (:,:,jk) = e3t_0(jk)
         e3u (:,:,jk) = e3t_0(jk)
         e3v (:,:,jk) = e3t_0(jk)
         e3f (:,:,jk) = e3t_0(jk)
         e3w (:,:,jk) = e3w_0(jk)
         e3uw(:,:,jk) = e3w_0(jk)
         e3vw(:,:,jk) = e3w_0(jk)
      END DO

By the way I'm not sure maintaining a specific zco option which is basically a particular case of zps really worth it, especially since we've suppressed key_zco and associated performance gain (we just have the ability to read a bathy_level file). Having zps activated, rn_e3zps_rat=1 and rn_e3zps_min big enough could make it as well.

[nicolasmartin]

Milestone 2012 Stream 1: User Interfaces deleted