Visit my TomShanahan.Report home page UNC PHOTO: Sam Howell threw for 3,586 yards and 30 touchdowns with only seven interceptions last year as a true sophomore. By TOM SHANAHAN CHARLOTTE, N.C. -- North Carolina may be new to boasting a Heisman Trophy preseason leading candidate, but venerable Tar Heels coach Mack Brown has a history of navigating that road over his 16 years at Texas. So, Brown didn’t fret over the offseason how to address the attention third-year…