occbin_write_regimes bug: smoothed regimes are not handled

the current behavior of occbin_write_regimes command points to the field oo_.occbin.regime_history, which is provided as a result of a model simulation. when running a smoother, instead, regime history is stored in oo_.occbin.smoother.regime_history: we would then need an extra option to the command to specify whether the regmies come from a simulation or from a smoother, so to allow calling it;

occbin_write_regimes(smoother); or occbin_write_regimes(simulation);

at this point, we may also think to move the results of a simulation in a substructure oo_.occbin.simul ?