v0.6.0 — sparkline interaction + native Excel sparklines

Hover a sparkline for a per-point readout; click a point to get sparklinePointClicked for drill-through; domain: 'group' scales within row groups. And the xlsx payoff: nativeSparklines: true exports sparkline columns as live Excel sparklines (hidden data blocks + x14 sparkline groups) instead of flattened text. See CHANGELOG.md.

npm add https://github.com/methodify/augrid/releases/download/v0.6.0/augrid-core-0.6.0.tgz \
        https://github.com/methodify/augrid/releases/download/v0.6.0/augrid-react-0.6.0.tgz