feat: adds features module with 2D spatial index and basic property utils

[edparris]

This change adds a new aws.osml.features module that will contain classes and functions designed to work with features derived from overhead imagery. As a start two classes have been added:

• ImagedFeaturePropertyAccessor: This class abstracts away the different GeoJSON property names various projects have been using (e.g. "bounds_imcoords", "geom_imcoords", "detection.pixelCoordinates", etc.) and provides a consistent interface for reading and writing those properties. This is a first step towards the proposed standard of "imageGeometry" and "imageBBox" properties.
• STRFeature2DSpatialIndex: This class is a 2D spatial index of GeoJSON features that will allow us to efficiently find features using spatial queries or nearest neighbor searches. The current implementation is based on a Sort-Tile-Recursive (STR) tree implemented by Shapely but a general Feature2DSpatialIndex abstraction has been provided allowing us to swap out implementations in the future.

This change does add a new dependency on the Shapely library to supply the geometry primitives used in this library. Shapely is already used by the OSML ModelRunner so this addition will not increase the overall dependency footprint.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[jtblack-aws]

Looks like we have a mix of camelCase and snake_case values - would we be able to standardize on one of them or is this driven by an external interface?

[edparris]

These are driven by external interfaces.

I agree it would be best to pick one convention and stick with it. At some point we may want to release a breaking change to remove the older values.