Combined Core and Rail Docker for rail based elements.

It would be nice to be able to create doors and other permanently docked rail creations without the need for a ship core. It would only save a single block, but that can be vital in small ships.

Also, it would be nice for the new combined core\docker, to be able to rotate without clearance at the corners. This would allow it to be embedded within small locations more easily.

Thank you for reading.