Remove entries from geospatial index (#633).

Once a Geo Coordinate topic is deleted (e.g. when an Address is deleted) the corresponding entry is removed from the geospatial index.

NOTE: this module is still experimental. Only use it with a testing DB.

See #633.

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CORRECT COMMIT MESSAGE FOR PREVIOUS COMMIT:

Update geospatial index (#633).

Once a Geo Coordinate topic changes (e.g. when an Address is changed) the geospatial index is updated accordingly.

See #633.