[bug 1088807] Fix Option A.

This is one way to fix the problem. But it makes for some ugly URLs.

Implementing a `ProfileFilter` is easy:

```
class ProfileFilter(django_filters.FilterSet):
    date_joined = django_filters.DateTimeFilter(name='user__date_joined')

    class Meta:
        model = Profile
        fields = ['date_joined']
```

But the ordering stuff doesn't look as easy. Do we want that?

r?