Refactor the process_station_measures to work on a per station key basis.
Refactor the process_station_measures to work on a per station key basis.

This lets us remove a bunch of the dictionaries and state tracking and
make sure we only check the blacklist and free space once per station.

mozilla/ichnaea,mozilla/ichnaea,mozilla/ichnaea,therewillbecode/ichnaea,mozilla/ichnaea,therewillbecode/ichnaea,therewillbecode/ichnaea