title: Add button to Unity3d editor
body: <p>In Unity3D, I can have a property field appear in the editor by simply adding a public property to the class. Is it possible to add a button next to this field that opens up a file browser that populates that field? </p>
  
  <p>I've found <a href="http://docs.unity3d.com/ScriptReference/EditorUtility.OpenFilePanel.html" rel="nofollow">EditorUtility.OpenFilePanel</a> but how can I add a button to call that method within the editor? (I don't mean a menu in the toolbar at the top as shown in the example code on that page)</p>
  
  <p>Thanks</p>