AP_Motors: added PlusRev motors type

this is a plus frame with reversed motor direction, needed for quad in
Morse simulator

libraries/AP_Motors/AP_MotorsMatrix.cpp

@@ -547,6 +547,14 @@ void AP_MotorsMatrix::setup_motors(motor_frame_class frame_class, motor_frame_ty
                     add_motor(AP_MOTORS_MOT_4, 0, 160, AP_MOTORS_MATRIX_YAW_FACTOR_CW, 2);
                     success = true;
                     break;
+                case MOTOR_FRAME_TYPE_PLUSREV:
+                    // plus with reversed motor directions
+                    add_motor(AP_MOTORS_MOT_1,  90, AP_MOTORS_MATRIX_YAW_FACTOR_CW, 2);
+                    add_motor(AP_MOTORS_MOT_2, -90, AP_MOTORS_MATRIX_YAW_FACTOR_CW, 4);
+                    add_motor(AP_MOTORS_MOT_3,   0, AP_MOTORS_MATRIX_YAW_FACTOR_CCW,1);
+                    add_motor(AP_MOTORS_MOT_4, 180, AP_MOTORS_MATRIX_YAW_FACTOR_CCW,3);
+                    success = true;
+                    break;
                 default:
                     // quad frame class does not support this frame type
                     break;

libraries/AP_Motors/AP_Motors_Class.h

@@ -52,6 +52,7 @@ public:
         MOTOR_FRAME_TYPE_H = 3,
         MOTOR_FRAME_TYPE_VTAIL = 4,
         MOTOR_FRAME_TYPE_ATAIL = 5,
+        MOTOR_FRAME_TYPE_PLUSREV = 6, // plus with reversed motor direction
         MOTOR_FRAME_TYPE_Y6B = 10,
         MOTOR_FRAME_TYPE_Y6F = 11 // for FireFlyY6
     };