Add SeqWho as alignment-free FastQScreen alternative

[MatthiasZepper]

Description of feature

SeqWho is another tool that allows to quickly corroborating the origin of sequencing reads, but in contrast to FastQScreen does not align to references, but uses a precomputed index and a classifier. Since there is also full support by MultiQC already, the tool could be a straightforward and useful addition to the pipeline.