Hg 88 pan/zoom

- pan in media lightbox
- doubltap to set scale to 3
- zoom with pinch
- pan while zooming
- still support swipe to next image, but only when not zooming
how come some events are camelCased and others aren't-- for instance, `swipeLeft` is camelCased but `panend` is not. I'd prefer them all to be camelCased.