Feb. 24th is opening day for our newest Aldi supermarket, next door to HomeGoods at White Flint Plaza. Aldi, which is poised to become the nation’s third-largest grocery chain, has long been known for its low prices and no-frills atmosphere. But in recent years, the German company has stepped up its image with better produce, a vast array of organics, and high-quality private-label brands. Aldi also has an army of super-fans who stalk its treasure-hunt aisles for limited-edition finds: crockpots, rain boots, picnic blankets, exercise bikes, furniture and other random products at crazy-cheap prices.