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.
`[01:42:37] <Phrohdoh> ProductionAirdrop should probably not notify cloning factories.`
Let me know what you guys think and how I could possibly expose this better in yaml.