Fix loggers and logging handlers
Created by: mguijarr
This PR fixes the exceptions eaten up by the root logger, which only had 'custom_log_handler' handler: exceptions were not printed on stdout, which made debugging a lot hardier.
It also comes with logging enhancements:
- custom_log_handler level is now INFO (instead of DEBUG).
- use same formatter for all log handlers
- use TimedRotatingFileHandler for (optional) log file, which aggregates all log messages
- all log handlers log to stdout and emit messages to web clients.