When `true`, the hotspot is scaled to match the fish eye effect of the image.

Hotspots then appear to be embedded in the panorama instead of floating on top

This resolves pixelation issues on some mobile devices (fixes #725).
It also may be related to issues #301, #496, #683, and #708.

For three event listeners added to the container elements weren't being
removed properly, since `removeEventListener` was mistakenly being called on
`uiContainer` instead. This was preventing garbage collection.

Add `stopMovement` to stop all movement