Filesync sets ownership/group of all files to root

[grayside]

• We want to be able to specify the uid/gid inside the container, but maintain expected user/group file ownership in localhost.
• Can we handle this via volume configuration? Or docker run uid mapping like docker-sync?
• If not, can we ad ad hoc settings to our docker-compose volume config, with fallback to the outrigger.yml config for sync?

This issue was already addressed in docker-sync: https://github.com/EugenMayer/docker-sync/issues/226