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
Something similar is used here: https://github.com/Wikia/mercury/pull/194/files#diff-0f2baee6dc3109f12b3a9ecd7f7e662cR76 can we extract and reuse?