Prevented the AI from building too many megastructures (hopefully). Improved the megastructure edict further to uncap arc furnaces and dyson swarms for players only.

Small patch to fix some flags meant to prevent some megastructures from being able to be built on top of each other.

Update: Fixed the issue where it was possible to build ringworlds on top of ringworlds together with some other cases where it was possible to construct multiple megastructure on top of the same star. It is still possible to have a ringworld together with any other megastructure at the same star. The only remaining case where a ringworld can stack on top of another ringworld is in binary/trinary systems. As constructing a ringworld on one of the side stars will always place the ring over the center star. So in binary max two ringworlds can be on top of each other and in trinary max three ringworlds.

Removed the 25 pop limit to construct an Grand Archive.