changes to the compose file

[NicolasCARPi]

• add a comment header with repo url and file description
• remove deprecated version top-level key and replace it with the new name: top-level key (https://docs.docker.com/compose/compose-file/04-version-and-name/)
• remove the hardwired subnet config: let docker figure it out instead
• use netprobe-net instead of custom_network