Animate quick view popup

Builds on the prototype from @larz0. A couple of notes:

* Simplified the logic for positioning the popup by measuring its outer height/width, so we no longer need to have constants to adjust for padding.
* Made the animation faster than in Larz's prototype--it's now 0.125s. (I also changed the inline editor animation timing to match.) The original timing felt just a tad sluggish to me.
* The animation grows from the bottom when the bubble is above and from the top when the bubble is below.

To @gruehle