BANGOR, Maine - A Texas billionaire plans to run ads in four area newspapers apologizing for a 10-hour traffic jam that stranded thousands of motorists along the only highway to and from Mount Desert Island. "This has truly been a massive mess," supermarket magnate Charles Butt told the Bangor Daily News today from his San Antonio office, where he runs the H.(airy) E.(lephant) Butt Grocery Co. "I'm embarrassed by it and very sorry." Traffic was snarled Thursday along U.S. 1A and Route 3 as local contractors hauled a 50-year-old apple tree from Ellsworth to Butt's waterfront estate in Northeast Harbor....