Realistic unit building

[Taqwus]

Regarding re-using ship designs, it'd be nice to see a "Downgrade" button that, for every currently unavailable component, would downgrade it to the most advanced Version available, or list a Warning about that specific component if no such Version at all was available. That way, one could keep the hi-tech Versions from finished game, ditch the obsolete ones, and then in the next downgrade followed by periodic upgrades when new tech is found.

------------------
-- The thing that goes bump in the night