Maintain robot status in mid-tier server

[tlau]

"central server for each robot that tracks which actions are going on (awareness both in smach_executer and in server mid-tier)"

Because web clients are flaky (disconnect, reconnect, reload, have multiple viewers at once) we want to have a central server that caches information about the robots (battery status, who's currently operating it, what it's currently doing, etc.) and provides this information to all web clients who request it.

[tlau]

The "also viewing" information only works when people are logged into the same server (e.g. babylon1). If I am controlling a robot using my server on localhost, this information is not propagated to other people using babylon1. The "also viewing" status should be stored on a single centralized server, not the local webserver.