clean up iiif output a bit
clean up iiif output a bit

better info.json, but still not support for the full/ directory

see https://github.com/libvips/libvips/issues/1465

lovell/libvips,jcupitt/libvips,jcupitt/libvips,lovell/libvips,lovell/libvips,jcupitt/libvips,lovell/libvips,jcupitt/libvips