AP_Motors: support dodeca-octa quad

[rmackay9]

At least one manufacturer has asked that we extend our dodeca-hexa copter support to cover dodeca-octa quads (e.g. 8 arms, 16 motors). Because of the number of wires required, we should probably follow the same motor order convention as is used for dodeca-hexa copters. E.g. front-right-top motor is "1" and spins CCW, front-right-bottom is "2" and spins CW, etc

[muramura]

@rmackay9 san. I am defining the motor layout for a 16-motor octocopter.

OUTO COPTER MOTOR LAYOUT https://ardupilot.org/copter/docs/connect-escs-and-motors.html#octo-frames

Motor 1 of the octocopter is CW (clockwise). The configuration follows this specification.

type: plus https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_Scripting/examples/MotorMatrix_hexadeca_octa.lua

type: X / cw https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_Scripting/examples/MotorMatrix_hexadeca_octa_cw_x.lua