Investigate alternate geo-grouping and storage schemes for OSM data

[jkoshy]

Investigate more cache efficient ways to group OSM elements.

"Real-life" usage (e.g., map queries from JOSM) appear to have a significant degree of geographical locality to them.

It may help to group OSM elements in a different manner, so that repeated queries in the same geographical area are served with fewer compute resources (and faster).

This ticket tracks the following tasks:

1. Collect data on actual data access patterns.
2. Implement a cache efficient grouping scheme that works well with these access patterns.

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