Discussion loading perf

This changes Discussion's initialisation and loading. It now loads comments sooner, rather than waiting for id and top comment calls to return.

Includes some general hygiene around the cta controller and the discussion bootstrap
It does use Bean's event delegation, underneath. Based on the container element. Not keen on the operator-overload style of it, though. https://github.com/guardian/frontend/blob/master/common/app/assets/javascripts/modules/component.js#L250