Sunburst of a taxonomic tree

The same taxonomy as concentric rings, one ring per level, so every depth is visible at once. Click an arc to re-root the sunburst on it. useFixedColors draws from a fixed palette instead of handing out colours in the order nodes are met, and fixedColorHash keys that palette on name and rank, so a taxon keeps its colour across datasets. getTooltipText replaces the default hit count with Unipept's own sequence counts.