Add support for monitoring of on-board temperature

[jvetter1]

The new phoenix board has an on-board temperature sensor that we are not taking advantage of.

This issue would:

• Add the code to monitor this temperature
• Optional: add way to view in LCD
• Optional: add support to view in PID Display
• Optional: add support to alarm when temp is too high

[jvetter1]

Pull Request References:

• brewtrollergit/brewtroller@c8d7ae7
• brewtrollergit/brewtroller@b215ad4