title: how to make group an drag in three.js?
body: <p>I made a plane and sphere, texture cube and simple cube and a loaded amf on it, how can I drag or pan the plane, and drag all the mentioned object togethor, actually I made group, and I helped from trackBallControl and OrbitControl.
  here are parts of my code, I don't know really what to do for it. I can drag seperately but not as a group.</p>
  
  <pre><code>var grid = new THREE.GridHelper(50, 50, 0xffffff, 0x555555);
          grid.rotateOnAxis(new THREE.Vector3(1, 0, 0), 90 * (Math.PI / 180));
          scene.add(grid);
  var grids= [grid];
  controls = new THREE.TrackballControls(camera);
  controls.rotateSpeed = 1.0;
  controls.zoomSpeed = 1.2;
  controls.panSpeed = 10;
  controls.noZoom = false;
  controls.noPan = false;
  controls.staticMoving = true;
  controls.dynamicDampingFactor = 0.3;
  var dragControls = new THREE.DragControls(grids, camera, renderer.domElement);
  dragControls.addEventListener('dragstart', function (event) {
  controls.enabled = false;
          });
  
  dragControls.addEventListener('dragend', function (event) {
  controls.enabled = true;
          });
  </code></pre>