The Songwriters Hall of Fame announced its class of 2018: Alan Jackson, Bill Anderson, Steve Dorff, Kool & The Gang (Robert “Kool” Bell, Ronald Bell, George Brown and James “JT” Taylor), Jermaine Dupri, John Mellencamp and Allee Willis. Three of this year’s inductees—Alan Jackson, Bill Anderson and Steve Dorff—have had a significant impact on country music.…