doc for set_vertical_localization_coord

[hkershaw-brown]

It does not seem to be in the add your model to dart documentation that
set_vertical_localization_coord() is required for models doing vertical localization. It is mentioned in a 2017 changelog, but that seems to be it.
Also a call to set_vertical_localization_coord() should go in the template model::static_init_model()

[hkershaw-brown]

Actually maybe not just a doc issue

There is no protection for vertical_localization_coord being unset (0)

DART/assimilation_code/modules/assimilation/assim_tools_mod.f90

Lines 483 to 484 in 4c89e64

	call convert_vertical_obs(ens_handle, obs_ens_handle%my_num_vars, my_obs_loc, &
	my_obs_kind, my_obs_type, get_vertical_localization_coord(), vstatus)