Traded eggs in gen4 can have from any game (since version isn't updated on hatch).
Use the hashsets, and remove the incorrect array. The incorrect array allowed stuff like Pokéwalker to be a "valid met location", hah.
held item list now allocates less (concat arrays instead of ienumerables)
item list already prunes out of range items, so simplify data source fetch
simplify item list prune (return as list, so we can call RemoveAll instead of Where.ToList)
