Function candidatesForHere

Build the candidate pool for the here neighborhood (req §11.2):

1. The location itself.
2. Each Detail on the location.
3. Doors associated with the location's exits (each door + details).
4. Each Exit on the location (direction + aliases).

Peers (the location's contents) live in their own seed — candidatesForPeers. here is the location's own surface, not the room's inhabitants.