Adjustments to Concentration Camps

[Dilvish]

Due to what has been a rather broken nature to Concentration Camps, Eleazar recently suggested we consider just commenting them out for now, until happiness is in. Before putting them on ice, I wanted to give a go at fixing them up reasonably so I went ahead and did that. They now work hand in hand with a couple associated specials, to help control the staging of the primary effect and to make sure that production does not remain artificially boosted after a Concentration Camp has been scrapped (which couldn't be managed with just the building specification alone). One of the specials also lingers for a while after a Camp is scrapped, still having a (lesser) negative effect on population for a random number of turns (averaging 8 ), so they are more risky to employ than before.