New module: FADU for quantification of prokaryotic RNA-seq

[JuliaMuench]

The FADU (feature aggregate depth utility, https://doi.org/10.1128/mSystems.00917-20) is a quantification tool designed specifically for prokaryotic RNA-Seq analyses.

Example tool output:
s1_fadu.counts.txt
s2_fadu.counts.txt

• This comment contains a description of changes (with reason)
• CHANGELOG.md has been updated

• There is example tool output for tools in the https://github.com/ewels/MultiQC_TestData repository or attached to this PR
• Code is tested and works locally (including with --lint flag)
• docs/README.md is updated with link to below
• docs/modulename.md is created
• Everything that can be represented with a plot instead of a table is a plot
• Report sections have a description and help text (with self.add_section)
• There aren't any huge tables with > 6 columns (explain reasoning if so)
• Each table column has a different colour scale to its neighbour, which relates to the data (eg. if high numbers are bad, they're red)
• Module does not do any significant computational work