title: Django Grapelli add autocomplete lookups on InlineAdmin
body: <p>I have this 3 models:</p>
  
  <pre class="lang-python prettyprint-override"><code>class MyFile(models.Model):
      file = models.FileField(upload_to="files/%Y/%m/%d")
  
      def __unicode__(self):
          """."""
          return "%s" % (
              self.file.name)    
  
  class ExampleModel(models.Model):
      attached_files =models.ManyToManyField(MyFile)
      main_model = models.ForeignKey(MainModel)    
  
  class MainModel(models.Model):
      attached_files =models.ManyToManyField(MyFile)
  </code></pre>
  
  <p>And my <code>admin.py</code> as follows:</p>
  
  <pre class="lang-python prettyprint-override"><code>class ExampleModelAdminInline(admin.TabularInline):
      model = ExampleModel
      extra = 2    
  
  class MainModelAdmin(admin.ModelAdmin):
      inlines = [ExampleModelAdminInline]
  </code></pre>
  
  <p>Im using <code>django-grapelli</code> because it offer autocomplete lookups for many to many fields. However, Im not sure how to add this autocomplete lookup to a <code>TabularInline</code> admin. Can anyone explain me how to set up the <code>attached_files</code> field to have autocomplete lookups?</p>