OSPRay v2.8.0

• Lights can be now part of OSPGroup and thus instanced like
  geometries and volumes and thus lights also support motion blur
  (with the path tracer)
• Add cylinder light (with solid area sampling)
• Add support for rolling shutter of cameras
• Add support for quaternion motion blur for instance and camera to
  allow for smoothly interpolated rotations
• Fix illumination from emissive quad meshes