Adds a number of predefined ProxyExit objects to adv3Lite, together with their associated SpecialTravelActions

This extension provides the code for doorways, passageways, paths and archways that may be mentioned in room descriptions but don't otherwise needs to be defined with separate objects (Doors, Passages, or PathPassages). Instead you can just define a TravelConnector, Room, method or string on the relevant non-directional property (doorway, passageway, pathway or archway) of the room in question, or else use the multiXXXway property of the room to say there are multiple such doors or whatever.