FIX: AutoCloseables are not called on servlet destroy (Fixes #119)

Author: xhanin

restx-core/src/main/java/restx/RestxMainRouterFactory.java

@@ -70,6 +70,7 @@ public static synchronized void clear(String serverId) {
         routers.remove(serverId);
         Optional<Factory> factory = Factory.getFactory(serverId);
         if (factory.isPresent()) {
+            factory.get().close();
             Factory.unregister(serverId, factory.get());
         }
     }