SACRAMENTO — The economic storm that has battered the North Coast wine industry since 2008 appears to be over.Three years of slumping wine sales finally hit bottom in 2010, analysts said Wednesday at the annual Unified Wine & Grape Symposium in Sacramento, the largest wine industry conference in the United States. High-end wine sales grew by double digits last year, said Danny Brager, who tracks wine sales for The Nielsen Company. Wine prices, which fell steadily throughout the first half of 2010, began stabilizing in the summer, marking a break in the intense discounting that gave consumers lower and lower prices.