* Implemented link creation based on link plans
* Improvised an implementation of door placement in DefaultDoorDecorator
for testing purposes. I'll provide a better version later.
Known issues:
1. Doors with one-way links to other rooms will generate a return door
at the destination. The return door doesn't actually lead back, it leads
to a new pocket. Need to disable pair generation for doors in mazes.
2. Consider weighing sections by the door capacity to avoid putting a
lot of doors into a small section. Also double-check that room selection
within sections is unbiased.
* Finished implementing link planning for mazes. Doors aren't placed yet
because that's up to Decorators and those haven't been implemented yet.
* Added bounding walls to mazes.
* Added decay effects to mazes.
