"Minnesota Highway Beautification and Scenic Preservation Act"; modifying certain provisions regulating the erection and maintenance of outdoor advertising devices adjacent to certain highways; expanding the definition of adjacent area; modifying a certain exception to the advertising device prohibition and authorizing the placement of star city and county and recycling center signs; including outdoor advertising devices in the provision under the fair campaign practices act regulating acceptance of paid political advertisements in newspapers, periodicals or magazines, requiring equal access to advertising space by candidates and ballot questions (ra)