MEET JAKE DRAKE,  KNOW-IT-ALL   Jake Drake is excited about Despres Elementary School's first science fair. He wants to win the grand prize: a brand-new Hyper-Cross-Functional Bluntium Twelve computer system. And he really wants to beat the third-grade know-it-alls, Marsha McCall and Kevin Young.   The trouble is, to beat the know-it-alls, Jake has to become a know-it-all himself. And he may just lose more than he wins.