Create a new Unsupervised-Discretizer

[MarvinGronhorst]

Since we did not find a non-GPL CRAN-hosted package, that discretizes continuous data in an unsupervised manner #44 , an unsupervised discretizer should be implemented directly. It could resemble the implementations of viadee in the 'javaAnchorAdapters' package. https://github.com/viadee/javaAnchorAdapters/tree/master/DefaultConfigsExtension/src/main/java/de/viadee/xai/anchor/adapter/tabular/discretizer/impl

Useful discretizers could be equalfrequency (PercentileMedianDiscretizers) and manual cutpoints (ManualDiscretizer).

and should discretize as shown in the tests:

https://github.com/viadee/javaAnchorAdapters/tree/master/DefaultConfigsExtension/src/test/java/de/viadee/xai/anchor/adapter/tabular/discretizer