Unless otherwise prohibited by specific statute or rule, informal disposition may be made of any adjudicative proceeding, or any part or issue thereof, by stipulation, settlement, waiver of hearing, consent order, default, alternative dispute resolution, or other informal disposition, subject to agency approval. Any administrative agency may adopt rules of practice or procedure for informal disposition if such rules do not substantially prejudice the rights of any party. Such rules may establish procedures for converting an administrative matter from one type of proceeding to another type of proceeding.