Verify external cache are working properly

https://www.drupal.org/node/2364011

(worth also checking https://www.drupal.org/node/2364011#comment-9291895)
how about keeping ``pageFooter()``, but only as a wrapper around ``drupal_page_footer``, and maybe move the current implementation to the docs under the "super-advanced-mateu-gone-wild" section? :P