PASADENA, Calif.- ABC news executives yesterday vowed to give Sunday-morning stalwart "This Week" a "freshening up" by airing stories that reach beyond Washington.The Beltway talk institution will take a new twist this September -- when solo anchor George Stephanopoulas takes control of the show that producers promised will connect general news stories to politics.And Stephanopoulas said he has a standing invitation for his former boss, President Clinton, to appear on "This Week."If the show's new format aired this week, producers said, stories like the Atkins diet or hormone gene therpy might be popular topics of "This Week"Freshening up, to us,...