export/hazard:

Use `iterator()` when fetching (potentially) large hazard curves, to avoid
caching them. This drastically reduces spikes in memory usage for the export.
export/hazard:

Slightly faster and slightly leaner (less memory usage) query for hazard
curve export.
export/hazard:

Updated HazardCurveData query to avoid returning and constructing millions of
Point geometry objects.
export/hazard:

When exporting hazard curves, order DB query results by `id`. This ensures
that results have a stable and consistent order.
Merge pull request #1008 from larsbutler/hc-export-optimize

Optimized hazard curve export

[r=matley] [f=1099763]