Added ClonesProductionUnits trait for RA2-style Cloning Vats

Yep we're in a feature freeze.
Yep we don't have RA2 yet.

I think mod authors will be happy to have this a few games early.
You can simplify and correct this block to:

```csharp
				var notify = self.World.ActorsWithTrait<INotifyOtherProduction>()
					.Where(a => a.Actor.Owner == self.Owner);

				foreach (var n in notify)
					n.Trait.UnitProducedByOther(n.Actor, self, newUnit);
```