config valitation

[vinzens]

So far there is no validation of the config.
The Ari-proxy does read the config and starts even though the config is invalid and the ari-proxy is not able to connect since there is an invalid connection for asterisk and kafka and/or the connection is not working.
If the ari-proxy is not able to function properly it must not start and stay started. A problem in startup must be logged at least to stdout (if logger config is broken) and the service has to terminate.