Remove OkHttp installation from GeoJSON download, and a bit of cleanup

This resolves #323. 

But GeoJSON drawing does not actually work right now, as best as I can tell. @bleege, can you comment on anything else I should do to restore GeoJSON drawing after downloading?

**Update:** It was just *my* GeoJSON drawing that wasn't working, because the parser as implemented only handles GeoJSON whose root element is either `Feature` or `FeatureCollection`. Mine are `MultPolygon`s all around.

This PR also fixes some linting errors and adds a couple logging lines, as described below.