By Denny Dyroff, Entertainment Editor, The Times  Clarence Spady Two highly acclaimed blues artists will be performing at the Sellersville Theater (24 West Temple Avenue, Sellersville, 215-257-5808, www.st94.com) in the upcoming week – Clarence Spady on July 2 and Ana Popovic on July 6. They couldn’t be less alike. Spady is an African-American male guitarist from North Jersey who now lives in...