Log configuration on proxy start

This has to simplify the debugging because usually we do not know all
options which user used to start mtg.

main.go

 	defer logger.Sync() // nolint: errcheck
 
 	printURLs(conf.GetURLs())
+	zap.S().Debugw("Configuration", "config", conf)
 
 	if conf.UseMiddleProxy() {
 		zap.S().Infow("Use middle proxy connection to Telegram")