Update smartsensor pin definitions for hardware PWM

Originally the pinout of the smart sensors did not have hardware
PWM pins used for servos or for the battery buzzer. Since it is
much easier to handle this completely in hardware, arrange the
pins differently to allow for this.
Implemented battery buzzer functionality

The battery buzzer sends voltage measurements to the controller board
as well as sounding an audible alarm if battery cell voltages are outside
an acceptable range.