Moved configuration out of the extra package.

Also improve some minor parts of the YAMLConf class.
Fix server list configuration.

As of 3bb30b8, field descriptions won't be implemented for now, I might
add this again later.
Improve comment writing.
Rename save to write in YAMLConf.

Those methods will only pass the YAML output to a writer, they won't
save anything in a file on their own. A correct save method would take
only a file or a path.
Remove lombok for now.
More configuration stuff.