[WIP] Implement new popovers

No issue

Implements a new popover component (not to be confused with what are now called dropdowns [menus])

Todo:

- [x] Emberify
- [ ] Get checked over by people with Über Ember skilz

togglePopover doesn't take `true/false` for its second param, it takes the popover that should be toggled. The popover will then be told to toggle. there's no jquery-style "toggle(true)/toggle(false)", just toggle()