Implement Variant calling pipeline

[Nicklas Nordborg]

The starting point can probably be Hisat alignments. It is not yet sure what kind of data that is going to be produced. We will at least get a vcf file containing found variants. It might be possible to attach this data to the current alignment item, but it may also be better to create a child item for this. A child item is better if we get a lot of data files and is also required if we want to re-run the analysis without overwriting the first result.

We can start building the framework for hooking into auto-confirmation and the manual wizards. It can probably be very similar to how the framework for the mBAF pipeline is implemented (#1068).