Disable Gifs: Unpause all gifs in photoset on hover?

[marcustyphoon]

I personally would much prefer if hovering over any paused gif in a photoset unpaused all of the gifs at once; if I want to see the animation of one of them, I want to see them all, and hovering each one individually is quite inconvenient, particularly when the GIFs are of a scene with dialogue.

This is nontrivial to implement, though, since there isn't a DOM element around a photoset; it's made up of multiple row elements in a rows element that also contains the rest of the reblog. Presumably we do not want hovering over the text below a photoset to unpause the gifs in the photoset; that sounds unintuitive.

Adding a wrapper element or an event listener on mouse movement both sound like bad ways to do this.

[marcustyphoon]

Note that this was implemented in #562.