Better whitelist and ops support in offline mode

[FedotCompot]

Enhancement Type

Improve an existing feature

Describe the enhancement

When online-mode=false OPS and WHITELIST users that are not found using playerdb.co should have UUIDs generated offline using something like this.

If necessary i can provide js and bash scripts that generate offline UUID from a nickname, it's some basic bit manipulation of the md5 hash of the nickname