AS-382, AS-404: Getting load balancers in structured form

Getting load balancer nodes and time they were drained from feeds using effect.
You don't need this map (or nodetype_map), by the way. You can just do `NodeCondition.lookupByName`. If you want to go the other direction, the individual constants have `name` attributes.

(If you don't want to tie constants to their names, then you can always use `twisted.python.util.Values` instead of `Names` :))