Feature syslog support

Added support for using syslog as destination for logging.

New parameters added:

```
  -s, --enable-syslog   Used to enable logging to syslog. Use -l to specify
                        syslog host.
  --syslog-host=SYSLOG_HOST
                        Used to specify the syslog host. The default is
                        'localhost:514'
  --syslog-facility=SYSLOG_FACILITY
                        Used to specify the syslog facility. The default is
                        'user'
```