Jackson: It’s been nearly two years since Gov. Charlie Crist told the state’s utilities to burn less coal for energy. The announcement set the scene for legislative pressure and the evolution of a buzz term: “20 by 2020.” That describes the potential mandate. In 11 years, 20 percent of the state’s electricity would need to be produced by sources like solar panels and wind turbines. Environmentalists have cheered the idea. At JEA alone, environmental program director Jay Worley …