Disqus comment count text, fix in Url::page

- If the Disqus script fails to load correctly, the **Comments** link at the end of the post is not visible (it has no text). This adds the **Comments** text to the link, which is replaced with the comment count by the script.

- The `Url::page($page, $absolute=false)` function returned the url relative to HTML_PATH_ROOT regardless of the value of `$absolute`