Bobby Rush’s new Down in Louisiana, out February 19, 2013 on Deep Rush Productions through Thirty Tigers, is the work of a funky fire-breathing legend. Its 11 songs revel in the grit, grind and soul that’s been the blues innovator’s trademark since the 1960s, when he stood shoulder to shoulder on the stages of Chicago with Muddy Waters, Howlin’ Wolf, Little Walter and other giants.Of course, it’s hard to recognize a future giant when he’s standing among his mentors.