Undertow subsystem enhancements

-  WFLY-3368 Better reverse proxy configuration
- Properly implement error-pages as filters 
- WFLY-3672 Add configuration to enable PeerNameResolvingHandler
- WFLY-3697 Custom filters support
not really, I had it in original impl, but then i moved to Map.
Thing is that filter resource as such needs to be complete having sub resources separately manageable doesn't really play nicely with concept of one resource = one service.

And together with new cli operations / tools for map manipulation there is really no need for separate resource.