title: editing multiple objects in gui with [CanEditMultipleObjects]
body: <p>I've created a unity Editor class, where I want to select my "tiles" and add "wall"s to it. It works for single selection, but I can't work it out for multiple selection. I found </p>
  
  <blockquote>
    <p>[CanEditMultipleObjects]</p>
  </blockquote>
  
  <p>but that alone won't help. Here's the Editor script:</p>
  
  <pre><code>#if UNITY_EDITOR
  using UnityEngine;
  using System.Collections;
  using UnityEditor;
  
  [CustomEditor(typeof(TileMorpherMonoBehaviour))] 
  [CanEditMultipleObjects]
  public class TileMorpher : Editor {
  
  public override void OnInspectorGUI() {
      TileControl tileControl = (target as TileMorpherMonoBehaviour).gameObject.GetComponent&lt;TileControl&gt; ();
  
      if (GUILayout.Button("Add wall")) {
          tileControl.addWall ();
      }
      if (GUILayout.Button("Remove wall")) {
          tileControl.removeWall ();
      }
  }
  
  }
  #endif
  </code></pre>