The spring of 2013 is here, sort of, and grain and soy futures markets turn toward analyzing prospects for the new crops that will be sown during the next several weeks. For some traders, this represents relief after many months of focus on drought-damaged U.S. production in 2012 and the subsequent squeeze on corn and soybean supplies that drove futures prices to very high levels -- and in some cases, record high levels. For other traders, the market's attention to potentially large 2013 crops in the U.S. and the rest of the Northern Hemisphere signals the end of a long-term bull market. It began in the second quarter of 2010, took a pause from the third quarter of 2011 until the second quarter of 2012, then roared off again until early t...