Adjust severity annotation color bar

[bschilder]

Priority: medium

The color bar showing the scale for the severity annotations should

• be discrete (0, 1, 2, 3) and only show these values, instead of continuous values that fall in between
• include the mappings onto what each of those values mean (0=never, 1=rarely, 2=often, 3=always)

Optionally, you may want to

• include an additional column showing the composite severity score on the righthand side
• make the color palettes similar to Fig 3 in our associated preprint