world.js: Introduce function to copy positions
world.js: Introduce World.VILLAGE_POS

This constant gets reused in a few places, so extract it out. Work will be
required to migrate existing code away from hard coding World.RADIUS in places
where we are talking about the village location.
world.js: Increase functionality of getDistance

Allow passing 'from' and 'to' positions to getDistance to find the distance
between them.
world.js: Improve road drawing algorithm

Instead of drawing an 'L' shape road to the village, find the closest road,
outpost or village and draw the road to it. Care is taken to ensure that a
road is drawn if you are standing on top of an outpost, as the outpost may be
created before the tile it stands on is connected to the road network.