After a tough year in 2012, solar stocks -- companies producing products that convert sunlight into electricity -- are starting 2013 at a gallop. Or so it would seem. As a group, solar stocks are up 50% since mid-November, rising to the top ranking among 197 industries tracked by IBD. A doubling of planned solar installation purchases in China and a $2.5 billion project funded by Berkshire Hathaway (BRKA) are among the drivers. It's a nice