Control of Märklin 74861 turntable & 72886 roundhouse doors with Rocrail

As an early adopter of the Märklin 74861 I found myself developing its integration with Rocrail. Fortunately, I was not the first. User acmezger did it before. My contribution has been to improve his work to spare unuseful half turns of the bridge. As a plus, I added the control of the roundhouse doors (Digikeijs DR4024 and servos), which open and close when needed.