Get rid of optaplanner-workbench-models-core in optaplanner repository (duplicates entire optaplanner-core source code)

I am not a fan of these 2 modules in this directory. I 'd rather see them disappear:
https://github.com/kiegroup/optaplanner/tree/master/optaplanner-integration/optaplanner-workbench-models

Especially the fact that optaplanner-workbench-models-core duplicates all optaplanner-core sources in target/core-dependencies and intellij automatically puts those in the classpath, causing massive "duplicate code" warnings is a pain.

Ideally, this new model, which uses the new tbroyer gwt plugin:
https://github.com/kiegroup/optaplanner/tree/master/optaplanner-integration/optaplanner-core-gwt
makes most (if not all) of optaplanner-workbench-models obsolete. But we need to check with Max Barkley when the workbench will move to the new tbroyer plugin (sooner rather than later).