Spatial 0.25-neo4j-3.2.5

Version 0.25 contains two primary changes:

• Addition of a GeoHash based index for point-only layers
• Change of license to GPL

The geohash index uses Neo4j's existing support for explicit string indexes, and follows the current pattern of manually adding nodes to the index during the layer.add operation. Each node will have its point location geohashed and the string result added to the index. Subsequent searches (including geopipes searches) will create a geohash prefix search against the index.

The change to GPL was something that should have been done back with Neo4j itself changed to GPL, however, it was overlooked at the time, leaving the spatial library using the AGPL (which Neo4j itself used before).