PID Mode5 - Fan-By-Servo

Adds new arduino code to allow the Fan speed to be conrolled by the servo being high or low positions.
Updates the Configuration page to allow selecting the new mode.

Should the Fan On at Max Only, Servo Full Open/Close Only, Fan-By-Servo be combined into a single drop down so only one alternate mode can be active at a time.

If you select both Fan On at Max Only & Servo Full Open/Close Only. You get a weird Bang-Bang controller. Fan-By-Servo ignores Fan On at Max Only and Servo Full Open/Close Only would probably do nothing.