Vcf symlink

This is a pretty junky script for Operations and/or data-transfer to symlink a bunch of build's SNV and Indel files. It is unclear to me how to test this so the test case is just a use of the module.
Builds that run DV2 inherit from 'Genome::Model::Build::RunsDV2' which defines accessors for the indel and snv vcf files:

get_indels_vcf
get_snvs_vcf

This is safer than hard-coding the current directory structure.