Video library has terrible performance

[yochannah]

At a guess, the YouTube iFrames for so many calls are what's whirring my machine up - in Firefox it's using over 6GB of memory and >100% CPU, and generally slowing down a reasonably powerful iMac.

Maybe we need to only load the youtube iframes (i assume they're iframes?) if the accordion is open?

@Tajuddeen1 @NPDebs this will be a js debug