Allow specification of owner and group for synced folders with type "rsy...

...nc"

Example how to set it up in config.yaml:

                rsync:
                    args:
                        - '--verbose'
                        - '--archive'
                        - '-z'
                    exclude:
                        - .git/
                    auto: 'true'
                    owner: 'www-data'
                    group: 'www-data'