Reinforce the test chamber some more so it can withstand TTBs and cannister bombs

[Berrik]

So, I decided just now to try to make a TTB, since I've never made a successful one before. Unfortunately, I'll never know if my bomb would have worked or not, because when I tried to test it in the test chamber, an admin disabled it and grumped at me, then told me the test chamber can't actually contain the force of bombs.

Which makes it kind of useless for it's intended purpose.

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Also make empty gas tanks craftable, please. We can make the big ones, why not the little ones?