djutils-base v2.4.1

The following issues have been resolved in djutils-base version 2.4.1:

Issue #23. Add category-based methods to CategoryLogger
Issue #24. Rename filter() method for CategoryLogger
Issue #25. Update documentation for logger class
Issue #26. Implement and test setting a different FQCN for the barrier in CategoryLogger
Issue #27. Add some getters to the CategoryLogger
Issue #28. Create unit tests for CategoryLogger formatter and callback

Note that Issue #24 causes a break with previous versions. Rename CategoryLogger.filter(..) to CategoryLogger.with(..)