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:

• https://github.com/brewtrollergit/brewtroller/commit/c8d7ae7882e27302115567fcc8bd88d8f6bcd604
• https://github.com/brewtrollergit/brewtroller/commit/b215ad40e863af0f5e0dad5ba8e6b53184f90c8a