Limit the Variant Abundance Estimate Outputs to Meaningful Accuracy

[gordonkoehn]

The current implementation of Lollipop outputs variant abundance with an unjustified numerical accuracy.

,city,estimate,variant,frac
2021-08-25,Lugano (TI),MSE,B.1.1.7,0.002713967329921789
2021-08-26,Lugano (TI),MSE,B.1.1.7,0.0026696935756146253
2021-08-27,Lugano (TI),MSE,B.1.1.7,0.002698547333990823
2021-08-28,Lugano (TI),MSE,B.1.1.7,0.0027834001206857406
2021-08-29,Lugano (TI),MSE,B.1.1.7,0.002902020246684484

Given we choose to output 95 % confidence intervals, and display to 2nd decimal on CovSpectrum.

I'd advise limiting precision to 2 decimals practically. Any more digits are meaningless anyway and only lead to flaky numerical stability issues, potentially.

[gordonkoehn]

Also, WiseDashboard quotes to this precision. So this would be a wider change.

[gordonkoehn]

Done in #19