Use a configuration management crate

[ISibboI]

A crate that easily allows to parse config files into a struct, while allowing overrides via CLI or environment variables for example.

• [ ] search for such a crate
• [ ] integrate it and replace the current cli if required

[ISibboI]

Possible options are:

• write it myself using serde and clap
• use config
• use config-derive

[ISibboI]

This does not seem important to do well for now, so it will be done later.

[ISibboI]

Simply using environment variables now