Auto 673 limit number of batch creation (ready for review)

Prevent the user from creating too many policies or webhooks at once.  I'm not too happy about having to reload the schema module if the pagination limits change, but perhaps that is ok for now?

Other option is to check the length in the REST handlers, and reject there.  Another option is to use a formatter, but since the json schema otherwise works fine for min, for array, for type, etc., I'd rather do it as it is here or to handle max length checking in the handler.