Nothing in this chapter shall be held to diminish the constitutional rights of any person, to limit or repeal additional requirements imposed by statute or otherwise recognized by law, to diminish any delegation of authority to any agency, nor to create any substantive rights; but this chapter shall be procedural. Except as otherwise required by law, all requirements or privileges relating to evidence or procedure shall apply equally to agencies and persons. Every agency is granted all authority necessary to comply with the requirements of this chapter through the issuance of rules or otherwise.