untagged-a558a9e16d59e5a9829a: Merge pull request #280 from scenerygraphics/ui-updates

UI updates:

* usage of flatlaf if run as standalone (https://www.formdev.com/flatlaf/)
* nicer inspector panel, which is collapsible to the sidebar
* nicer REPL panel, which is also collapsible to the sidebar

Also adds a new command to load Cremi datasets and segmentations, which is the first Kotlin-powered command 🥳