Since we have both version/version.go and version/VERSION to specify
version strings, both are a bit redundant.
As version/VERSION is supposed to be the source of truth now, we are
using it to derive the version informaiton we used to rely on in Packer
and its subcommands.
Note: doing this prevents us from changing the version/prerelease
through ldflags though as we derive Version/VersionPrerelease from the
rawVersion variable.
Lucas Bajolet
93bec31ec9