message: re-enable and fix PLY sg importer
diff: namespace ospray {
  namespace sg {
  -#if 0
  namespace ply {
  using std::string;
  using std::cout;
  @@ -136,9 +135,9 @@ namespace ospray {
  int file_type = 0;
  - std::shared_ptr<sg::DataVector3f> pos = std::make_shared<sg::DataVector3f>();
  - std::shared_ptr<sg::DataVector3f> nor = std::make_shared<sg::DataVector3f>();
  - std::shared_ptr<sg::DataVector3i> idx = std::make_shared<sg::DataVector3i>();
  + auto pos = createNode("vertex", "DataVector3f")->nodeAs<DataVector3f>();
  + auto nor = createNode("normal", "DataVector3f")->nodeAs<DataVector3f>();
  + auto idx = createNode("index", "DataVector3i")->nodeAs<DataVector3i>();
  /*** Read in the original PLY object ***/
  const char *filename = fileName.c_str();
  @@ -337,23 +336,20 @@ namespace ospray {
  free(ply->elems);
  - mesh->index = idx;
  - mesh->vertex = pos;
  + mesh->add(idx);
  + mesh->add(pos);
  if (!nor->v.empty())
  - mesh->normal = nor;
  + mesh->add(nor);
  }
  } // ::ospray::sg::ply
  -#endif
  void importPLY(std::shared_ptr<Node> &world, const FileName &fileName)
  {
  -#if 0
  - std::shared_ptr<sg::TriangleMesh> mesh =
  - std::static_pointer_cast<sg::TriangleMesh>(sg::createNode(fileName.name(), "TriangleMesh"));
  + auto mesh = sg::createNode(fileName.name(),
  + "TriangleMesh")->nodeAs<TriangleMesh>();
  ply::readFile(fileName.str(), mesh);
  - world->add(std::dynamic_pointer_cast<sg::Node>(mesh));
  -#endif
  + world->add(mesh);
  }
  } // ::ospray::sg
  