wptagent log local logs syslog rfc5424

[FedericoMulas]

ref 177487

• Added log handler for syslog rfc5424 to support structured logging, ported from https://github.com/jobec/rfc5424-logging-handler/tree/master with BSD license because seems frozen and had needed issues pending (only 2 files where needed).
• Added new RotatedFileTransport(StreamTransport) in internal\rfc5424logging\transport.py to support an external tool rotating the log file (e.g. logrotate, logstash, etc.).
• Added new file rfc5424logging_context.py and relative class LoggingContext to store structured logging context to enhance each log while keeping backward compatibility with other types of logs.
  * Added additional option --loglevel and refactored log level option handling into setup_logging class to support current log format an the new introduced rfc5424 log format.
• Added additional option --logformat and refactored log level option handling into setup_logging class to support. It reuse --verbose option and --log to set the log file path and verbosity. Only supports new introduced rfc5424 log format syslog.

After this PR is approved all log entries will be updated to add the new logging context.

[mjkozicki]

@pmeenan If you could take a look, thanks.

[pmeenan]

Mostly LGTM but the flag behavior is a bit confusing. It might be cleaner to always use verbosity to set the log level and just use a different flag to switch logging into Rfc 5424 mode. That way log file and verbosity params would be consistent. I'm good either way though.

[pmeenan]

nit, is not None is core consistent python with the existing code
if logging_level is not None and log_file is not None:

[FedericoMulas]

@pmeenan I refactored as suggested, works well too.