Make some techs exclusive for certain races

[Xyquas]

I like the randomization feature implemented in Horizon's research mechanism. But I think it's a bit lame that every race can research every tech if it just spends enough RP. I'd like to see some techs that are exclusive to certain races so that I'm forced to get these techs via diplomacy (or invasion if this feature is added) or to play the game without them.

Exclusive techs should support race traits, so that good merchants (Barsig) get an extra merchant tech, good fighters (Tantik) maybe get an extra ground combat unit, good environmentalists (Barbeck) get extra terraforming or waste disposal and so on. I could imagine changing availability of some current techs. Maybe there should be limits in engine and weapon techs.