Utility API to verify which environment is the web application running.
The utility will check initially for the existence of a system property under the name `vertx.mode`,
if there is no such property then it will look under the environment variables under the name `VERTX_MODE`.
This value will be then used when the API is invoked. By itself this utility will not
affect the behavior of your application, however you can use it to simplify your handlers, e.g.:
When the development mode is active you can log more information or disable caches.