re-enable and fix PLY sg importer
re-enable and fix PLY sg importer

ospray/OSPRay,wilsonCernWq/ospray,wilsonCernWq/ospray,ospray/OSPRay,MengjiaoH/ospray,ospray/OSPRay,ospray/OSPRay,MengjiaoH/ospray,MengjiaoH/ospray,MengjiaoH/ospray,MengjiaoH/ospray,wilsonCernWq/ospray