By Denny Dyroff, Staff Writer, The Times Selwyn Birchwood Frequently, mid-week can be a slow time for live music. Such is not the case this week at the World Café Live (3025 Walnut Street, Philadelphia, 215-222-1400, www.worldcafelive.com) which has a high-powered blues act on Tuesday evening and a top-flight blues/rockabilly show on Wednesday. A few weeks ago, Selwyn Birchwood released his new...