Move cacheable_article out of article view
Move cacheable_article out of article view

This makes it reusable by other views than just the article view. It is
renamed to _cacheable_article to signify that the function is not a view
that should be linked to directly by a url mapping.

stianjensen/wikipendium.no,stianjensen/wikipendium.no,stianjensen/wikipendium.no