Allow servers to proxy

[MicahParks]

Proxy pubsub servers should be implemented.

A central pubsub server could be at site A and a user's proxy pubsub server could be at site B. This would allow multiple subscribers at site B to get the same subscriber information with multiple connections to the proxy pubsub server at site B, but only one connection to the central pubsub server at site A.

Considerations:

• One proxy server may make multiple connections to the central pubsub server. One per subscription topic. If this can be reduced to one connection, that would be best, but a control channel may be required for that, which is undesired.