Move ugly debug to Settings  Labs

 closes #4534

- Adds new Labs route
- Wires route in settings page
- Move and rename debug templates and logic to labs
- Redirect /debug to settings/labs
As far as I can tell the only place it's ever referenced is in `test/unit/config_spec.js` as a test to just make sure it exists--haha.  So, I'm thinking it it can probably just go away.