Abstract Restlet server creation

I've been wanting to integrate camel-restlet with WildFly-Camel for some time. The sticking point has been getting consumers running on WildFly's native undertow server.

Similar to what we did with the Undertow component, I'd like to create some abstractions for how the restlet component creates servers. The default implementation can create a Restlet server instance and I can provide my own implementation for Undertow in WildFly-Camel.