External configuration via `config.json` placed in the root dir

This allows a better individual configuration for the loggers
Externalized public ip resolver.

config.json can hold property „publicIpResolve“ which is for example `{„enabled“: true, „url“: „http://resolve.me“}`. http://resolve.me has to return just the text of it’s remote ip address.
Merge pull request #4 from knalli/feature/external-configurablity

External configuration via `config.json` placed in the root dir