dune predictor only for movable bed

The dune predictor gives the calculated roughness value back to telemac. This is not useful in case of rigid bed. For real case applications typically there are parts where a dune predictor doesn't make any sense. A first good choice would be to take the roughness coefficient from gaia only if there is a movable bed. Another possibility (maybe additionally) would be to add to the roughness file (*.tbl) a field per friction ID whether the value from the dune predictor should be taken or not.