services/pubsub: setup topic & subscription on deployment

[mgenov]

The thing that bothers me for pub/sub usage on local environment is that there is no automatic way for update of topics and subscriptions on deployment.

Here is an init servlet that updates topic and subscriptions but it requires a remote client to call it.
https://github.com/GoogleCloudPlatform/cloud-pubsub-samples-java/blob/master/appengine-push/src/main/java/com/google/cloud/pubsub/client/demos/appengine/servlet/InitServlet.java

I though that google-appengine-plugin could deal with this stuff as it is authenticated and is able to use the pubsub api. What you guys think about this topic ?