Any person who wilfully violates any provision of this act or directs or consents to such violation, is guilty of a misdemeanor and, upon conviction thereof, may be punished by imprisonment in the county jail for a period not to exceed 90 days and may be fined not more than $500 or both for the first offense; and for each subsequent offense a like fine or imprisoned not to exceed 1 year, or both. Violation of any order, decree or injunction issued pursuant to the provisions of this act shall constitute prima facie proof of a violation of this section.