title: Unity3D How to using AssetBundle.LoadAsync direct load prefab from Assets folder
body: <p>Can i using AssetBundle.LoadAsync direct load a prefab from Assets folder?
  in Assets/Bundle folder has a prefab called "BGELement" , i did not want put it in to Resources folder and using Resource.Load to load it. 
  the follow is my code ,but it make a error : NullReferenceException, the error line is that ab.LoadAsync()</p>
  
  <pre><code> using UnityEngine;
  using System.Collections;
  
  public class Test : MonoBehaviour {
  
      void Start () {
          StartCoroutine(NewLoadBGElement ());
      }
  
      IEnumerator NewLoadBGElement () {
          string path = Application.dataPath + "/Bundle/BGElement";
          AssetBundle ab = new AssetBundle ();
          AssetBundleRequest abr = ab.LoadAsync(path, typeof(GameObject));
          yield return abr;
          GameObject newCube = Instantiate(abr.asset) as GameObject;
      }
  }
  </code></pre>