LOS ANGELES (Reuters Life!) - Onions make you cry, add flavor to food and are touted for their medicinal benefits. Now the vegetable has another use -- powering up green energy.A new system debuts on Friday that converts onion juice into electricity at Gills Onions, the largest fresh onion processor in the United States. The Oxnard, California-based company expects its new onion-fueled power to reduce its electric bill by $700,000 a year and cut its annual greenhouse gas emissions by up to 30,00