Feature/extended environment support

[mooseh]

Summary of work

• removed version from docker-compose.yml (no longer supported in docker compose)
• added better spacing for readability against wget command
• added docker-compose example to readme
• added addition environment variables to control server config behaviour
• added envsubst package to allow for direct env to config support
• added defaults to the top of the entrypoint in favour of sed replace
• added custom.cfg by default to the server.cfg to lead users to use a permanent non templated config

Notes

this PR has been tested and works as inteded.
the exposed key was just for testing and have bene revoked.