Defining business income and redefining nonbusiness income for income tax purposes; providing for taxpayer election for treatment of all income as business income, election to be irrevocable for a certain number of years and to be binding on all members of a unitary business; prohibiting the commissioner of revenue from treating business income reported in pre-1999 tax years as nonbusiness income, voiding commissioner adjustment, assessment or reduction orders subject to administrative or judicial challenge (ra)