REFACTOR: Fixes poor class hierarchy for listing topics

- Upgrades Ember to latest
- Fixes a bunch of bugs with page titles and missing "active" states
Lots of bugfixes

BUGFIX: navigation bar should always activate the right tab (even when diging into a top period)
BUGFIX: /top pages titles
BUGFIX: no "edit category" button on /top page after visiting a category
BUGFIX: properly hide category columns when there is no children category (on both filter + top pages)
BUGFIX: promises not caught when scrolling down a topic list to load more of them
BUGFIX: CSS on category dropdowns
Updated `top_menu` i18n with available filters