Explorer: tour the world and leave notes

A tool to explore every location and leave comments for improvements: teleport to a place on the atlas or to coordinates, a capture with each comment, the atlas inside the game.

Done: uo-client --explore, the in-game map (M), go to (G), notes with captures (N), walking the open notes (J / K) and resolving them (U). Follow-up: explorer-overlays.