Multibillion-dollar mergers, stock market fluctuations and consumer spending patterns tend to grab the business headlines, but there is a quiet force that pumps a steady stream of revenue into the nation's economy.It's the nonprofit sector, and its impact in Douglas County is significant, a recent study shows."Nonprofits boldly go where no government or business dares to go," said Joe Roszak, director of Riverside Center in Winston. "The reason being, government can't go there because it's too expensive and businesses won't go there because there's no money. We are the bridge to meeting significant needs of a community that aren't financially …