Datum pool no longer creates a new object just for the sake of it when initializing pool lists.
Also bandaids an issue where water could be qdeled while being sprayed and reagents nulled, because someone calls spawn() qdel in new.
Datum pool now also adds excess pool objects on the trash pile instead of calling del directly.
Grilles no longer return more rods than they were created from when destroyed (by method other than wirecutters).
Rods are now acquired from and returned to a pool.
Also adds a pre-broken grille for mapping, avoids the case where one might be able to destroy the same grille twice.
