Modified tag common_helpers.make_articles_list

The tag now accepts kargs for filtering and exclusion, apart from
sort strategies. Usage is:

make_articles_list "sort1" "sort2" filter=v1 exclusion__ne=v2

This will, in principle, become:

Articles.objects.filter(filter=v1).exclude(exclusion=v2)\
    .sort("sort1", "sort2")