Provide and end-to-end HTTP/2 proxy soultion with load balancing based on application server feeback

It should be possible to set up end-to-end HTTP/2 reverse-proxied connections with load balancing based on metrics fed back from the JBoss application server.

The "end-to-end HTTP/2" part is achievable by using mod_http2, mod_proxy_http2 and mod_proxy_balancer, however this does not provide the "metrics from JBoss" part.

The metrics part is achievable through mod_cluster, however this does not allow end-to-end HTTP/2 connections as per JBCS-327.