Made the RecursiveDirectoryWatcher thread a daemon (#2957)

Author: me4502

worldedit-core/src/main/java/com/sk89q/worldedit/internal/util/RecursiveDirectoryWatcher.java

@@ -235,6 +235,7 @@ public void start(Consumer<DirEntryChangeEvent> eventConsumer) {
             LOGGER.debug("RecursiveDirectoryWatcher::EventConsumer exited");
         });
         watchThread.setName("WorldEdit-RecursiveDirectoryWatcher");
+        watchThread.setDaemon(true);
         watchThread.start();
     }