As Digital Sandbox KC was getting started earlier this year at Union Station, a new business accelerator was opening its doors right across the street. SparkLabKC offers a fast-paced experienced for entrepreneurs, with three months of “heavy mentoring” that helps startups to tune up their strategies, work on their prototypes and refine their pitches. The first class included 11 companies, and the accelerator’s first-ever Demo Day took place in late…