Plat 556 http rest proxy watching

When using this to watch (eg, etcd) it's difficult for debugging to have to catch exceptions, and we need to get data as it comes, not only once the connection is closed.

These changes allow for the HTTP Rest Proxy to be used in this context.
This seems to turn HttpRestProxy into a both sync and async http client. Would it not be better to use the HttpClient class instead, which was meant to be asynchronous from the start?