public void stop() {
        if (null != periodicTickTask) { stopTask(periodicTickTask); }
        if (null != periodicTickExecutorService) { periodicTickExecutorService.shutdownNow(); }
    }
Calling this method will stop all threads. This is needed when using
JavaFX on mobile devices when the device goes to sleep mode.
src/main/java/eu/hansolo/tilesfx/Tile.java