title: Prepopulate django filter horizontal in admin
body: <p>I have a simple Django project about tennis network. And I would like to prepopulate a filter horizontal in my admin interface with the name of player. Also, some player can play at 7PM and the others at 9PM. My <strong>model.py</strong> is as follow :</p>
  
  <pre><code>class thursday(models.Model):
      date = models.DateField()
      time_first = models.ManyToManyField(player, related_name='firsttime', verbose_name='7PM')
      time_second = models.ManyToManyField(player, related_name='secondtime', verbose_name='9PM')
  </code></pre>
  
  <p>and my <strong>admin.py</strong> :</p>
  
  <pre><code>class ThursdayAdmin(admin.ModelAdmin):
      list_display = ('date', 'status')
      search_fields = ['date']
      filter_horizontal = ('time_first', 'time_second',)
      list_filter = ('date',)
      fieldsets = (
          (None, {
              'fields': ('date', 'time_first', 'time_second', 'status')
          }),
      )
  </code></pre>
  
  <p>Obviously, I would like to prepopulate the "time_first" filter horizontal with only player which can play at 7PM, and idem for the second.
  How is it possible to do that?</p>
  
  <p>Thanks in advance.</p>