By Denny Dyroff, Staff Writer, The Times Seth Walker Seth Walker’s show on May 11 at MilkBoy Philly (1100 Chestnut Street, Philadelphia, 215- 925-6455, www.milkboyphilly.com) may have a large city downtown location but the vibe inside the venue will be country – with a healthy dose of the blues. Over the past 10 years, Seth Walker has become recognized as one of the most revered modern roots...