Been investigating PID idle control in 1.2.13

Some issues found.

Proportional operating when IAC is inactive.

Seems like stall prevention, needs itīs own P term for proper calibration

"IAC close delay" (TPS > IAC threshold) overrides all other duty cycle values and is able to shut of the valve completely.

Some engines need a minimum airflow otherwise they stumple at low TPS positions and it maybe very difficult to control the pedal at such low loads.

min pwm is only so that PID values canīt force the valve so closed that it stalls the engine (I windup/down). Even better would be a configurable offset to the DCref value so that engines with light flywheels are less likely to stall coming to idle speed.

In Vemstune someplaces say minmap, other lowmap, needs to be clearer if they are the same or not.

Assymetric PID Conf needs explaining.

Advance rate of change is a P value not a rate value and therefor needs a new name.