Graylog: Integrate with Log{Client,LogMonitor}

Graylog: Integrate with Log{Client,LogMonitor}

Adds graylog/GELF logging support to clog and monitor log.

Changes to Graylog class:
- Support Logging LogEntry classes
- Add parameter "logger" to indicate the log source
  (e.g dlog, clog, mon)

New config opts:
- clog to graylog
- clog to graylog host
- clog to graylog port

- mon cluster log to graylog
- mon cluster log to graylog host
- mon cluster log to graylog port

Signed-off-by: Marcel Lauhoff <ml@irq0.org>