Fixed pathfinding-related bug, made code hideous

Fixed a bug with the apparent front door position, still not sure why it
wasn't working before. Will need to go back and investigate. Also made
sure that all houses generated were fully navigable, and that front
doors didn't spawn at intersections. Well, I think. It might not have
worked.

Next up, fix the pathfinding so it doesn't go kaput if two NPCs
meet. Maybe turn off NPC + NPC collisions?