title: Django admin: use checkboxes in list view in list_filter()
body: <p>I have a model <code>Transaction</code> with a ForeignKey to another model (<code>TransactionState</code>) on <code>state</code> field. So in <code>admin.py</code> I have:</p>
  <pre><code>class TransactionAdmin(admin.ModelAdmin):
      ...
      list_filter = ('state', )
      ...
  </code></pre>
  <p>In <code>TransactionState</code> I have records like &quot;paid&quot;, &quot;unpaid&quot;, &quot;delivered&quot;, &quot;canceled&quot;, Etc. and it works fine but I want to be able to filter using checkboxes to allow multiple selection like &quot;paid&quot; OR &quot;delivered&quot;. It's possible?</p>