Revert "Removed preview world button."

This reverts commit 817ad88c3798617e66bc59fb2499433afc88fe69.
Revert "Removed UIDialogPreview, because it is not compatible with the world generation refactoring (or even possible anymore? :/) Sorry."

This reverts commit 1e069c77413be51982e17a692afee5a3f59480d5.
Fix blocks not getting the correct "basedOn"
Refactor the world preview feature to Core
Fix door not correctly finding assets