motor slider fixes and fix motor output in vm

sim/state/motornode.ts

@@ -17,7 +17,7 @@ namespace pxsim {
         private speedCmdTime: number;
         private _synchedMotor: MotorNode; // non-null if synchronized
 
-        private manualSpeed: number = 0;
+        private manualSpeed: number = undefined;
 
         constructor(port: number, large: boolean) {
             super(port);

sim/state/output.ts

@@ -97,6 +97,7 @@ namespace pxsim {
                             motors.forEach(motor => motor.stop());
                             return 2;
                         }
+                        case DAL.opOutputPower: 
                         case DAL.opOutputSpeed: {
                             // setSpeed
                             const port = buf.data[1];