By Denny Dyroff, Entertainment Editor, The Times The Whitmore Sisters It will be a family affair when the Whitmore Sisters open for the Mastersons on March 21 at City Winery (990 Filbert Street, Philadelphia, citywinery.com/philadelphia). The Whitmore Sisters — Eleanor and Bonnie Whitmore — are two of roots music’s most accomplished songwriters/instrumentalists/vocalists. The Mastersons...