By Denny Dyroff, Entertainment Editor, The Times Charlie Hunter & Lucy Woodward It’s summertime and things just keep rocking hard at Kennett Flash (102 Sycamore Alley, Kennett Square, 484-732-8295, http://www.kennettflash.org). The popular venue in Kennett Square started the weekend with a show Friday night by Heather Gillis, a young Nashville-based blues rocker from Florida. On July 14,...