Collectively, sisters Shelby Lynne and Allison Moorer have released 24 albums. Not Dark Yet, arriving Aug. 18, will be their first collection released together. Produced by Teddy Thompson, the 10-song collaborative effort offers new arrangements of The Louvin Brothers’ “Every Time You Leave,” Jessi Colter’s “I’m Looking for Blue Eyes,” Townes Van Zandt’s “Lungs” and…