[#943] replace logback with log4j

[bmarwell]

fixes #943

logback was probably added for tests or out of ignorance of the existing log4j dependency.

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[fpapon]

We also need to remove the logback.xml file in main resource and replace it by a log4j2 default config file

[bmarwell]

We also need to remove the logback.xml file in main resource and replace it by a log4j2 default config file

Please check if the config works for you (by executing the app manually, for example). Thanks for pointing me to this oversight! 👍🏻