Config 1.7 Logging

Currently, this is implemented in Perl only. For GO and Java, since they are using internal web server, it is more efficient and flexible to use the built-in server-side logging functions.

Log    example: {"Minlevel": "Emergency", "Maxlevel": "Info", "Filename": "/tmp/debug.log"}

If key Log is defined,  debugging messages will be dumped to local file at Filename. There are seven levels of logs: emergency, alert, critical, error, warn, notice, info, debug. The higher the level is, the more the messages it dumps.