Update the default log level to "INFO"

[BECATRUE]

Feature you want to implement

A user seems to use the logger app to check if the submission runs well.

So I think updating the default log level from "WARNING" to "INFO" is more efficient as the submission log level is "INFO".

[BECATRUE]

How about your opinion? @kangz12345

[kangz12345]

I think it is a matter of taste. For now, we are not quite sure of our system's stability, so "INFO" level logs are very informative. However, later they might seem too verbose.
So I suggest passing the default log levels (for both GUI and file) to the logger app constructor, so we can give them in the config file.