removed: ab_from_ct, bfrq_ct, coriolis, change, gpoly16ct.m, grav, djackett/indx

did not modify calls to mld.m/nanmld.m (waiting for new version of these scripts), but substituted call from mld/nanmld to gpoly16ct by call to gsw_rho_CT_exact

Modified optimize_surface_exact to return an additional argument (ithist), that stores iteration history of various variables for postprocessing.