title: How to remove an app from a django projects (and all its tables)
body: <p>I want to remove an app from a django project.</p>
  
  <p>I want to remove</p>
  
  <ul>
  <li>the tables of the app</li>
  <li>the content-types</li>
  <li>foreign-key usages of these content-types</li>
  </ul>
  
  <p>Running <code>manage.py migrate app_to_remove zero</code> does not work:</p>
  
  <pre><code>django.db.migrations.migration.IrreversibleError: 
  Operation &lt;RunPython &lt;function forwards_func at 0x7ff76075d668&gt;&gt; in
              fooapp.0007_add_bar is not reversible
  </code></pre>
  
  <p>I guess there are several migrations which are not reversible ...</p>