Plot dupRadar boxplots

[ewels]

The current MultiQC plot for dupRadar is a little tricky to interpret.

Instead of plotting the dotted line from this plot as is done currently:

Plot the median values from this boxplot:

Needs these values extracting in the R script. Can then plot with the custom_content module if the output syntax is done properly.

[Hammarn]

Is this something that we want @ewels? And should we aim to have that in the next milestone?

[ewels]

Yes, if the data is easy to find.

[ewels]

This issue was moved to nf-core#68