WIP: Change backup to be websockets-centric.

This is a slightly more focused version of #412 that also incorporates making the switch from POST-based requests to the websockets-based RPC.  In fact, this patch built out with that switch as the starting point rather than using the env-storage change as the starting point.

Currently this patch is incomplete.  However, the intention for the moment is the get feedback on the approach before investing more time.