title: Celery: list all tasks, scheduled, active *and* finished
body: <p><strong>Update for the bounty</strong></p>
  
  <p>I'd like a solution that does not involve a monitoring thread, if possible.</p>
  
  <hr>
  
  <p>I know I can view <em>scheduled</em> and <em>active</em> tasks using the <code>Inspect</code> class of my apps <code>Control</code>.</p>
  
  <pre><code>i = myapp.control.inspect()
  
  currently_running = i.active()
  scheduled = i.scheduled()
  </code></pre>
  
  <p>But I could not find any function to show already finished tasks. I know that this information mus be at least temporarily accessible, because I can look up a finished task by its <code>task_id</code>:</p>
  
  <pre><code>&gt;&gt;&gt; r = my task.AsyncResult(task_id=' ... ')
  &gt;&gt;&gt; r.state
  u'SUCCESS'
  </code></pre>
  
  <p>How can I get a <em>complete</em> list of scheduled, active and finished tasks? Or possibly a list of <em>all</em> tasks at once?</p>