Add support for ingesting osmChange documents #14
Description
Incremental updates to the map are distributed by the OpenStreetMap project in the form of OsmChange files. These need to be supported by the ingestor tool.
Open Issue: OsmChange files do not contain <changeset> elements; for now, the ingestor would need to fetch these elements from an upstream server.
See also: issue #22 which tracks related changes to the front-end.