UndertowJaxrsServer: Exposing the ability to add prefix paths to the server root path handler

Undertow allows adding a variety of paths, but the default behavior in the current UndertowJaxrsServer automatically registers a root handler and implicitly adds the JAX-RS defined paths to it, disallowing manually adding other paths. I am proposing exposing a method for the manual addition of other paths such as for serving static resources (e.g. web pages, API documentation) alongside the REST endpoints.

Inspired by a discussion I found when trying to find a solution to this problem: http://lists.jboss.org/pipermail/undertow-dev/2014-February/000680.html