The default portal margin is stored in the RoomManager. Previously this was propagated to Portals when the value was changed, and Portals each stored this default value.
This caused a bug during loading, if the RoomManager was loaded before Portals, the value was never propagated.
This PR makes the default margin a static value stored in the RoomManager, and the Portals now read directly from the static value when required, and do not store locally. This gets around the problem.