BREAKING CHANGE: Make file ownership opt-in

[ckulka]

This PR stops changing the file ownership of the Baikal folder upon container start.

This used to be required to ensure local volumes on the host have the correct permissions set and that the user id of nginx/httpd can access them. Nowadays though, the recommended approach is user re-mapping, see https://docs.docker.com/engine/security/userns-remap/.

Only breaking change as it changes default behaviour. Functionality is still available and can be enabled if required.