[hm] Only allow writing of the 2 extra bits on the LCD via digitalWrite
[hm] 20130604B 24966 bytes
[hm] Fix units resetting to default if not passed.

Thanks Remco Kortekaas
[hm] Add LEDSTIMULUS_AlarmAny
[hm] Revert: Move default units selection to pid class instead of config loader
[hm] Add 'A' pid units for raw ADC output
[hm] Fix PRR not being available on mega2560
[hm] Remove pid.outputMode, servo and fan now both run at the same time

This moves the servo to digital pin 8, atmega pin 14. As a side effect,
the maxFanSpeed no longer defines the upper limit of the PID output.
PID now always runs 0-100 and the fan speed is scaled between them rather
than simply clipping at maxFanSpeed. This may require some adjustment
to the PID constants to scale the output back up proportionally.
[hm] Remove servo control from Rev A hardware, it uses the LCD_DATA pin and would f that up
[hm] Replace INVERT_* flags with PIDFLAG_*

PIDFLAG_FAN_ONLY_MAX -> Only turn on the fan (to max) if the pidOutput is
100%. That is, only use the fan when the servo isn't enough.

PIDFLAG_SERVO_ANY_MAX -> The servo is either fully closed (at pidOutput=0)
or fully open (if pidOutput is not 0)
[hm] Standardize all output displays to use PIDOutput rather than FanSpeed
[hm] Fix servo opening slightly between every PID cycle caused by reusing ICR1
[hm] v3.1 boards must have their shift register cleared before sending digitalWrite auxPins ad-hoc

Thanks Dave Peart
[hm] Increase default servo range to 600us-2500us, seems to be standard for 1500us-centered servos
[hm] 20130729B 25030 bytes