By Kirsten Ferguson/For The Leader-Herald Fifty years ago this Friday, DJ Kool Herc threw a back-to-school party at 1520 Sedgwick Ave. in the Bronx — a moment in time now regarded as the birth of hip-hop. Events planned around the world this summer commemorate this important musical and cultural milestone. In the Capital Region, a new exhibit at Albany Center Gallery on view through Sept. 2, “Can’t Stop, Won’t Stop: Celebrating 50 Years of Hip Hop,” features the work of more than 25 regional artists depicting what this anniversary means to them. “I’m sure this is true for a lot…