#241 Add article_permalink directive to index controller

This is not a permalink. The URL for an article or page can be changed at any time.  You should use the string representation of the ID. This should create an URL that looks like: http://[SERVER]:[PORT]/article/23tjw561

The article controller already supports this. See: https://github.com/pencilblue/pencilblue/blob/master/controllers/article.js#L39