Use multiplier for motor PWM

[jeff-winn]

As a user being able to swap out equipment is helpful for reducing cost. The current values used by the PWM signals are specific to the motor driver being used.

Rather than using a hard value in the code, use a multiplier instead with the actual value coming from the config file on the SD card.

[jeff-winn]

Related to #90

[jeff-winn]

Most likely the config file will need to store a percentage between 0 and 100 to indicate the motor strength. This value would be used in defining the percentage of the motors for the flywheels and the pusher.

The motor controller min and max defines the actual values specific to the driver/ESC being used that gets multiplied by the percentage to determine the actual value fed into the PWM generator.