Add support for a VERSION file in the repo

And make the version available to the operator for comparison use.

The version params are the same as what we use in gitaly: https://gitlab.com/gitlab-org/gitaly/blob/master/internal/version/gitaly_version.go

This is the version we will tag when it's ready. And my intent is to have the operator only watch gitlab objects that are labeled with a matching version.

Part of: https://gitlab.com/charts/components/gitlab-operator/issues/29