Ready for visualization testing page

* Moved DOM head elements to load from script
* Fixed last slider not showing
* Tweaked CSS shadow
CSS linked externally.
JSON linked externally (from Github)
Attempt at fixing the CORS error
Reverted externally linked JSON
Re-arranged/refactored to prepare for implementation of dynamic loading of controls (tags and users)
Controls now dynamically loaded from user_data.json
Added labels.
UI tweaks
Fixed the addition and removal of group elements in the DOM
External links for test page.