Add a prepper house with a gunsmithing garage (CR)

I'm thinking we need more interesting trapped houses, so I made one. It's got a trapped front living room, and fortified backend, with a good amount of gunsmithing loot in the garage, and some canned goods on shelves. Opinions on the balance and such? I think I may make a "carpet landmine" trap to replace the blatant ones right now, but I couldn't find the location of the location of identstring to make a new trap.

Edit: oh, and I bumped up spawns in prepper basements (which was originally intended when I first did that, but I messed up the spawn syntax) and moved the gunsmithing itemgroups to the generic itemgroups.json for use in this house as well.
Yeah, these should technically have been their own PR but you at least mentioned 'em in the OP.  I agree that the balance needed tweaked there, so these won't block merge.