Include a coverage heat-map above amplicon graphic for each sample

[rambaut]

This would be a bar that runs along, just above the amplicon display, above the genome. It would show the which bits of the genome have coverage above the defined thresholds (as used in the coverage over time plots). Could be a red, yellow, green? Black for zero, red for 0 - 20x, yellow for 20x-100x, green for > 100x (very green for > 200x?).