[PR] Adds a shelterfrog spacebux purchase

[Ikea]

I want to see shelterfrogs back however I'd much rather see it as a trait instead of a spacebux purchase. To me spacebux are meant for silly little things, not major character traits. Not to mention, unless you fix the non-sheltergrog related issues that lead to it's removal in the first place, I don't think it really matters how the mutantrace is obtained if it can be obtained regularly. If those issues are fixed however, you might as well just make it into a trait then.