Boy Battles Back from Painful Burn Injury   PALMER, ALASKA-- Forest Gore, 12, battled back from a painful burn accident to become high scoring forward on his youth soccer team. In 1983 the youth fell backwards into a burning stump row, burning 50 percent of his body, much of it requiring grafts of pigskin. Doctors said Forest would be lucky to walk again. In the game at bottom, he scored five out of six of his team's goals.