@Override
    public Class<? extends IRegistry> getRegistryClass(IPluginRegistry pluginRegistry) {
        return loadConfigClass(getClassname(config, GATEWAY_REGISTRY_PREFIX),
                IRegistry.class, pluginRegistry, null);
    }
Engine configuration, read simplistically from Vert'x JSON config.

@see "http://vertx.io/manual.html#using-vertx-from-the-command-line"
@author Marc Savy {@literal <msavy@redhat.com>}
gateway/platforms/vertx3/vertx3/src/main/java/io/apiman/gateway/platforms/vertx3/common/config/VertxEngineConfig.java