Import RxJava versions of Vert.x classes

Use delegate on a “Rxified” vertx instance

To call a method expecting a io.vertx.core.Vertx instance when you have a io.vertx.reactivex.core.Vertx one, call the method. Verticle’s start() method needs to be adjusted when creating an instance of WikiDatabaseService:

@Override
  dbService = io.vertx.guides.wiki.database.WikiDatabaseService.createProxy(vertx.getDelegate(), wikiDbQueue);