Several changes to how data is stored in GeoFire

- Geohash length changed from 12 to 6 with no loss of accuracy. The
bounding box can take at most 6 characters so the extra ones were just
wasting bandwidth.
- indices node now looks like <geohash>:<key>
- Locations stored at [lat, lon] instead of “lat,lon”
- Updated all tests to the new format