Fix cargo loading/unloading.

- Fix the unloading subcell bug, letting us have units move to directly adjacent cells.
- Have the cursor change to a deploy-blocked cursor if the transport can't unload due to terrain type.
- Add RenderTransport for transport door opening.
- Remove turning/opening in general.

mods/common/lua/actor.lua

@@ -80,7 +80,7 @@ Actor.Hunt = function(actor)
 end
 
 Actor.UnloadCargo = function(actor, unloadAll)
-	actor:QueueActivity(OpenRA.New("UnloadCargo", { unloadAll }))
+	actor:QueueActivity(OpenRA.New("UnloadCargo", { actor, unloadAll }))
 end
 
 Actor.Harvest = function(actor)