Set Indexing Kind in geometry to whatever it is set on the server.

[rshura]

When the server is started with the non-default indexing option (through env var), the geojson.geometry indexing is still the default QuadTree. This means that the clipped polygons will not be indexed like stored polygons.

This PR fixed this issue.

[tidwall]

Rather than changing the globally shared geometry.DefaultIndexOptions of the geometry package, I recommend creating a field in the server type and passing it to the Clip() function, or other functions that call geometry.New*(). This will ensure that we never override other dependencies that may use the geometry package and expect that the DefaultIndexOptions doesn't change.

I added a PR #545, which is effectively the same as this one.

[rshura]

This sounds good to me! Let me close this one, in favor of #545.