Make all exits reachable
Make all exits reachable

The current system only places ramparts on the paths.
Sometimes walls can't be reach and the repairer gets stuck.
Instead of checking for each wall, check if each exit is reachable.
If not place ramparts on the path.

Fixes #4

Nevrdid/screeps,TooAngel/screeps,Jirajha/screeps,stu43005/screeps,stu43005/screeps,Jirajha/screeps,Nevrdid/screeps,TooAngel/screeps