Need automatic recovery of Arduino sensors

[mikebotts]

If any Arduino sensors lose connection to their OSH node, they currently have to be phyiscally restarted even after the hub is re-established. We need for the Arduino to auto-recover after a disconnect. Apparently in the Arduino library the sensor driver shuts down the sensor when it receives a negative response when trying to push a observation result to the hub. Perhaps we can instead ignore the negative response and keep sending new data values. That way, when the server recovers, the sensors will still be sending real-time data, resulting in automatic recovery.

This issue is based on experience from Tim Haynie after his server crashes, but it should also help with temporary mis-connects between an Arduino sensor and its hub.

extension of #4