Improve comment regarding restrict_incorrect option for feature selection within moses
Remove metapopulation::merge_nondominated_iter (it hasn't been used for a while)
Constify metapopulation::merge_nondominated (because it can)
Remove moses::scored_combo_tree, as it is not used anywhere
Renamed some moses types to be more up to date or simpler

penalized_behavioral_score -> penalized_bscore
composite_behavioral_score -> composite_penalized_bscore
bscored_combo_tree -> pbscored_combo_tree