Add output docs for all non-default modules.

[jfy133]

Currently only default MultiQC modules are described, for both GeneralStats and sections.

Modules to be added:

• bowtie2 [draft drawn]
• malt <- [draft drawn] column required: % Metagenomic Mapped
• kraken
• picard markduplicates [draft drawn] <- column required: duplication rate
• mtnucratio <- only column name, number of 'mt' mapping reads for each non-mt mapping read
• sexdeterrmine [draft drawn] <- columns required: Rate X, Rate Y
• multivcfanalyzer [draft drawn] <- columns required: % Hets

@ZandraFagernas I will send draft images when I've done them.
@TCLamnidis can you please draft something for SexDet, and also a sketch for Zandra

[TCLamnidis]

• Nuclear contamination <- columns required #snps, estimate and error.
  Currently working on it