Summertime nostalgia, romantic look backs at what might’ve been and reflecting on the halcyon days of youth. Written, directed, produced by and starring Edward Burns (“The Brothers McMullen,” “She’s The One,” Epix’s “Bridge and Tunnel”), the new drama, “Summer Days, Summer Nights,” is definitely sentimental for the past, the mistakes made, the loves found, and the friendships and seminal moments in our life shared.