Support for 'as' in template tag

[glezos]

django-pagination supports the 'as' keyword in the template tag:

{% autopaginate f.qs 40 as filter_list %}

This allows us to use it with django-filter too, as noted here: http://github.com/alex/django-filter/issues#issue/13.

To combing django-sorting with pagination, if I understand correctly, we'll need to do this:

{% autosort f.qs as actionlog %}
{% autopaginate actionlog 30 %}

Currently I'm doing this through the view, passing an extra argument to the template, but it'd be nice if we could provide this backwards-compatible fix.

[lukeman]

I started implementing this and realized that someone else already has a patch downstream (it looks to have been submitted to jezdez's fork).

http://github.com/jezdez/django-sorting/commit/9a67c3668c4235e4e542cc02a786c06168415f19

It's working well for me, but there is an additional bug that keeps django-filter from working properly. I am writing that up currently.