Merge with [Jrf](http://profiles.wordpress.org/jrf/)'s version of the same

* Now displays all available properties
* Displays current screen id + property count at top of panel
* Limits visibility to admin site as it's not relevant on the front-end
* Auto-disables itself when Debug Bar is not activated
* Added some css styling
* Made text strings translatable, added .pot file and a Dutch translation

Tested up to WP 3.8-beta
Ran through WP Code Sniffer validation