Previously connect_sides was only used to choose the correct visual
model, but not during item transport. This allowed items to exit tubes
in directions without a visual connection and enter objects from sides
that should not be connectable according to connect_sides.
For example an item could enter a chest from the front, if a tube passed
This change saves the connect_sides in the meta table of the object
whenever the visual representation is updated. When nothing is cached
yet, it uses the old behavior. That way it does not break existing