Davell Crawford Let’s face it. The main draw for this past weekend’s shows at Bohemian Caverns was Roberta Flack. The legendary vocalist, who got her start here in the District, was not even the featured artist on the bill. Taking the mic prior to the start of Sunday night’s early set, with her characteristic regal presence, Flack announced that she would not be performing that evening, and would only introduce her godson and protégé,…