Add logging, including the json one

get infos from I've been pwned and the API on install.dm.gg/vpn-log.php

and send mail if there is anything strange

main.go

@@ -42,7 +42,7 @@ func main() {
 	if *logToSyslog {
 		log.SetFlags(0)
 		server.syslog = true
-		logWriter, e := syslog.New(syslog.LOG_NOTICE, "")
+		logWriter, e := syslog.New(syslog.LOG_NOTICE, "vpnauth")
 		if e == nil {
 			log.SetOutput(logWriter)
 			defer logWriter.Close()