More train fixes

- No passing plastic flaps
- Only human based mobs can board trains
- Adjacent checks for exiting vehicles
- Cleaned up as many direct loc moves as possible
- Places removed cells in the removers hand

code/modules/vehicles/train.dm

@@ -68,8 +68,7 @@
 
 	if(user != load)
 		if(user in src)		//for handling players stuck in src - this shouldn't happen - but just in case it does
-			user.loc = T
-			contents -= user
+			user.forceMove(T)
 			return 1
 		return 0
 
@@ -93,8 +92,7 @@
 		return 0
 
 	if(user != load && (user in src))
-		user.loc = loc			//for handling players stuck in src
-		contents -= user
+		user.forceMove(loc)			//for handling players stuck in src
 	else if(load)
 		unload(user)			//unload if loaded
 	else if(!load && !user.buckled)