Added rudimentary GPS backup
Added rudimentary GPS backup

The web database now has lat/long for the planet posts, so we agreed we
can use GPS as a fallback. GPS will not be trusted if a beacon’s been
seen until no beacons have been seen, so as not to be inaccurate near
DCI where we should lean on beacons more.

rationalagents/dciplanetwalk,rationalagents/dciplanetwalk