Lane editor

[bhousel]

This is kind of a stretch goal, but we do hear from people that displaying and editing lane information would be really impactful to support.

Lots of discussion here from back in the iD days: https://github.com/openstreetmap/iD/issues/387

(Also we should find a way to restore the Turn Restriction editor, see #503)

We either need to create more GL contexts / Pixi Renderers, or find ways to display these things on the main map.