Copy ordering from Django queryset when wrapping in a search adapter

[nealedj]

Currently this will work:

    search_qs = SearchQueryAdapter.from_queryset(AModel.objects.all())
    search_qs = search_qs.order_by('-foo')

But not this:

    qs = AModel.objects.order_by('-foo')
    search_qs = SearchQueryAdapter.from_queryset(qs)