Multiplayer friendly.

GPM Compatibility

Added spawning the extra-galatic clusters

Added warning around custom planet classes, updated civic description and added planetary diversity unique planets

Added event that sets the ring_world_built flag on existing savegames.

Added ringworld_built flag to star if starting with ringworld for gigastructures.

Fixed bug where alpine worlds did not transfer

Added deposit to ringworld start to prevent rush to crystals/motes