Hey everyone,

I started using Laminar CI for my personal server, but I had trouble
with the current system service. My server is configured to only allow
members of the "git" group access to the Git repositories, so the CI
job running as the "laminar" user couldn't do anything useful. This
patch adds a new configuration field for a list of supplementary
groups to be used for the "laminar" user and the service process.

- Dave