Bunch of crew AI bugfixes/improvements:

- replacing empty oxygen tanks
- fixed characters only fixing leaks in the outer hull
- prioritizing large leaks over small ones
- fixed characters doing nothing after fixing all the leaks (and sinking to the bottom if they happen to be outside)
- more accurate welder aiming
- AIObjectiveGetItem makes the characters go to the cabinet/container an item is inside, not to the actual item (which may not be actually positioned at the container)

Subsurface/Source/Map/Gap.cs

@@ -38,6 +38,8 @@ namespace Barotrauma
 
         public Door ConnectedDoor;
 
+        public Structure ConnectedWall;
+
         public Vector2 LerpedFlowForce
         {
             get { return lerpedFlowForce; }