Update4wd and gear ratio

[mjstn]

This updates the standard Magni codebase with many improvements and options not present in the past as follows:

• Publish a motor_state topic to show low level motor currents and individual wheel positions and rotate rates and pwm drive
• Adds a pid_control setting to enable special modes in the firmware mostly of value for 4 wheel drive modes
• Adds a 'drive_type' to yaml config file that defaults to 'standard' (also the current firmware_default value). Can be 4wd
• Adds a 'wheel_type' to yaml config which defaults to 'standard' but for some custom hardware can be set to 'thin'
• Adds a wheel_gear_ratio' to yaml config that is normally 4.294. We may use other wheels where this is 5.17
• Adds a 'fw_max_pwm' to yaml that hard sets max PWM value set in firmware as a cap for illegal states

Other assorted improvements to log status info and some other things come in with this 'large' update.

[mjstn]

A few minor things have been pulled into this due to it taking a while to get reviewed. Nothing all that big. I have added comments around the cm.update call because this HUGE mystery is totally 'glossed over' and EXTREMELY complex so a nice fat comment is rather important.