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

Do popovers really need their own service? They can't just share the functionality with the `dropdown` service? This looks like a lot of code duplication that we don't actually need. I think the popover should just continue to do `this.get('dropdown').doShit()`, as opposed to `this.get('popover')`