varlociraptor/varlociraptor: Version 2.5.0

Allow definition of re-usable expressions in scenarions (via a new key "expressions:", see https://varlociraptor.github.io). Remove ability to parallelize Varlociraptor via --threads. This never properly saturated the given cores and caused some overhead. Instead, we recommend to parallelize in scatter/gather style via rbt vcf-split, see https://varlociraptor.github.io). resolution: can now be skipped in scenarios. For continuous universes, this will then assume a resolution of 100, for discrete universes resolution isn't used anyway