Remove insect spawning under thick roof

[sabrt00th]

Hey Aaron,

just wanted to pitch my two cents in after trying your mod out for a few days. For me, personally, I feel there should be some sort of incentive to research and build thick roofs; if a thick roof acts exactly like a regular mountain roof, creepy crawly insects included, then why would players bother to go through the hassle of spending ~12000 research points when they could just deal with the insects with old-fashioned steel and lead and research something more valuable?

If you do end up reading this, I'd massively appreciate it if you could consider adding this into the next update of the mod.

Cheers,
sabrt00th