Make it possible to enable debug logging for selected packages

[bianchi2]

Currently, there's no way to provide own log4j.properties. Even though logs level can be changed in runtime, it'd be great to be able to define log level for selected packages.

Perhaps it's worth adding a configmap which is mounted as a file to WEB-INF/classes? Even though charts allow defining additional volume mounts and volumes, one needs to create a configmap with log4j.properties, mount it into the right path in the container and reference configmap in an additional volume (which is obviously) some work to do.