Send real-time Humidity sensor readings to the Command Center dashboard

"As a Command Center leader, I need to see the live Humidity value for each firefighter in the current event, so that I can determine when it's appropriate to remove them."

* Assuming humidity reading are coming from the DHT22 sensor, that sensor will already be wired up as part of story #102 (so this story may involve less hardware effort and similar firmware effort)
* Sensor data to be transmitted from the device to the cloud
* CC web app to display the sensor readings for each firefighter registered in this event.

Questions:
* In story #102 we were only concerned about sensor data frequency to assist testing (e.g. every 5 seconds to avoid waiting). In this story, sensor data should be updated as per what will be needed in production. so (1) How often should this be? and (2) Is it the same for all sensors?

**Current Design Draft [may change]**