[PR] reduces construction times, allow building multiple girders at the same time.

[Superlagg]

Maybe making multiple girders on the same tile add those girders to the first girder on the tile, and do the easter egg thing to that one girder. Adding more girders wouldnt increase the hitpoints or anything, just fully repair that girder and add more metal sheets to it, so when its destroyed it'll throw out a lot more metal.