public WorkerTask<I, P, R> addFeature(final WorkerTask.TaskFeature<? super I, ? super P, ? super R> feature) {
        synchronized (taskMutex) {
            feature.accept(this);
            return this;
        }
    }
Adds a feature to this WorkerTask (e.g. {@link ProgressDialogFeature})
main/src/main/java/cgeo/geocaching/utils/workertask/WorkerTask.java