Implement new popovers

No issue

Implements a new popover component (not to be confused with what are now called dropdowns [menus])

Todo:

- [x] Emberify
- [x] Get checked over by people with Über Ember skilz
- [ ] Remove temporary code in debug view (when the rest of the code is all good)

If you change the initializer below to insert into these guys "dropdown" rather than "popover", you won't need to duplicate this code (ditto for willDestroyElement below). Much better solution imoz!