removed deadlocks in JavaFXUI
The JavaFXUI is a STA. Calling blocking methods can / does result in a deadlock: the CommandStack wants to execute a Command, but this is not possible because it needs to execute some stuff on the JavaFX thread, which is blocked by a abort/undo/redo/pause/resume request.
Fix: all abort/undo/redo/pause/resume calls are executed on another thread, therefore the UI thread is not blocked.
Additionally, abortOrStopGame is always called because it is possible and prevents concurrency issues