default pipeline target will be Vaxrank outputs based on the MHC predictor and somatic variant callers specified in the provided config. Asking for any other Vaxrank output (ie different variant callers from what's in the config) will result in an error.
config changes: user must specify MHC predictor, variant callers. Also, reference genome paths now point to zipped files
expanded unit test: will run Snakemake pipeline directly, also will try to run the Docker entrypoint script (in dry-run mode)
added some checks to the docker entrypoint script: checking user-specified targets
Among those: