varlociraptor workflow compatibility

[dlaehnemann]

This PR changes the column names in config/samples.tsv and config/units.tsv to match those of the dna-seq-varlociraptor Snakemake workflow. This way, parts of this workflow can be included as a module there, using the same samples.tsv and units.tsv prepared for that workflow.

To make this work, the samples.tsv and units.tsv parsing in common.smk is adapted, as are wildcard names throughout the workflow. While at it, I also tried to make some wildcard names more descriptive and constrict more wildcards to the values they can actually take.