The entrance to 1020 G Street NW in March when West Elm still occupied the space. Photo by r.m.b. We had been hearing whispers that the huge new Forever 21 at 1020 G Street NW would be opening up this weekend. But thanks to an email advertising a sale at the location, we can now confirm that the grand opening for the chain’s first D.C. location will be on Saturday, July 17 at 10…