Restore old centralized functionality to dedicated servers

Allow dedicated servers to behave like the old "centralized" version did: The server remembers which players were part of a prospect, and what workshop items were extracted from the prospect (regardless of by who). When a player joins a server, if a prospect the player was a part of has been completed, they receive any ren & exotic rewards generated (via the extant mail system). If a player's workshop items were extracted by different player, they are "mailed" back to the owner and returned when the owner connects to the server again.