dflib-jupyter: integrate Logback, allow to change log levels in notebook

[andrus]

We need an easy way to change log levels when working in Jupyter:

• Set the default level to WARN to avoid logging things like SQL statements to the console.
• Add API to DFLibJupyter to change this to more verbose logging.

To achieve this we'll likely need to swap slf4j-simple to logback as the logging provider. It allows changing levels in runtime:

 LoggerContext context = (LoggerContext) LoggerFactory.getILoggerFactory();
Logger logger = loggerContext.getLogger(packageName);
logger.setLevel(level);

While this introduces a new dependency, it removes an equally bad dependency on slf4j-simple , so it won't make things worse on balance.

[andrus]

Reopening due to the iJava classpath issue described here: SpencerPark/IJava#63 (comment) ... Once the issue is addressed, we can patch it back per attached diff:

61-diff.txt

[andrus]

This should already work with JJava kernel. However, let's decide, maybe this should be a part of JJava , not dflib-jupyter.