flowclient.get_geography columns

[Thingus]

Is your feature request related to a problem? Please describe.
When we're using geojsons returned from fc.get_geography to render reports, we need to join pcods to human-readable columns by hand

Describe the solution you'd like
To specify the columns included in the geojson for fc.get_geography.

Describe alternatives you've considered
Pulling the pcod-human mapping from flowdb directly, adding an extra flowclient method to grab the mapping.