Color by sampling year

[kimandrews]

Description of proposed changes

Since we're not inferring a timetree, this PR allows visualization of the sampling date by:

• Enabling coloring by sampling year
• Allowing sampling date to appear when clicking on tips and as a filtering option

Example output: https://nextstrain.org/staging/tb/colorbyyear

These changes are similar to those made to the rabies repo:
https://github.com/nextstrain/rabies/pull/12/commits

Related issue(s)

This addresses part of #34, but does not address recency coloring

Checklist

• Checks pass
• Update changelog

[jameshadfield]

Code looks good (but didn't test)

If you change the (auspice-config) coloring to be categorical you can display the legend in different ways, but it's a little more work as you would want to define the ordering of the years so that they're chronological. This is what I did for ebola

[joverlee521]

+1 for James' suggestion of using categorical display of year to avoid the weird 2007.99 display in the legend.

I think it should be straight-forward to copy the get-year.py script from ebola and use it here. (This would also adhere to our Snakemake style guide to avoid run blocks)

[jameshadfield]

I think it should be straight-forward to copy the get-year.py script from ebola and use it here.

One improvement (which I have been meaning to make there): rather than suggest a colouring block for the JSON, write them out in a colors.tsv which (I think!) will still result in the desired legend ordering.