The Fourth of July weekend will forever signify a special anniversary in the history of the Grateful Dead as this is when the surviving core members got together for a blowout 50th anniversary celebration that kicked off today (July 3) two years ago at Chicago’s Soldier Field. Flanked by Trey Anastasio, Bruce Hornsby and Jeff Chimenti, Bob Weir, Phil Lesh, Mickey Hart and Bill Kreutzmann took…