Added a debug block at the bottom of each page - based on a user preference

The debug view will only show if the *user preference  dev-debug* is set to true.

Currently only shows the time the page was rendered (to help debug caching issues).

![debug](https://f.cloud.github.com/assets/76709/323363/ba3c6dfe-9aaf-11e2-856a-532fbaffe9a2.png)