Refactor multi-resource UI and transfers

tests/_craft_menu_preview.gd

@@ -13,13 +13,16 @@ func _ready() -> void:
 	GameState.extractors.clear()
 	GameState.transporters.clear()
 	GameState.rocks = 180
+	GameState.gas = 36
 	GameState.fleet_cargo = 24
+	GameState.fleet_gas_cargo = 12
 	GameState.unlocked = ["shipyards", "logistics", "freight"]
 	var main: Node = load("res://Main.tscn").instantiate()
 	add_child(main)
 	main.get_node("BuildingField").place(GameState.BUILDING_SHIP_CRAFTER, Vector2(400.0, 0.0))
 	var crafter_id: int = int(GameState.buildings[-1].id)
 	GameState.deposit_to_building(crafter_id, 42)
+	GameState.find_building(crafter_id).gas_stock = 18
 	var bc: Node = main.get_node("BuildController")
 	bc.craft_building_id = crafter_id
 	# The shared header (#24) is the thing worth eyeballing here, so give it