Dave Dahl may be the unlikeliest person to build a brand around.The president of Dave's Killer Bread spent 15 years in prison for burglaries and other crimes to feed a methamphetamine habit. Growing up, he worked in the bakery started by his father in Portland in 1955, but he had no interest in making a career there.Now, Dahl is the public face of a company that has reported explosive sales in recent years. Part P.T. Barnum, part Dale Carnegie, part Jack LaLanne, Dahl presents a gripping story of personal destruction, growth and redemption. It's helped propel Dave's Killer Bread into …