[CR] Nerf of fire extinguishers

- First: too many charges.
A small fire extinguisher looks imbalanced: it's lighter than a big one (53g per charge vs 57g per charge), and 20 charges (=20 extinguished tiles) it's too big area for this small fire extinguisher.

Actually, the big fire extinguisher should be nefred too, because it can extinguish unreasonable huge area.

Current weight "cost":
Big fire extinguisher: 4535g / 80 = 57 g per charge;
Small fire extinguisher: 1062g / 20 = 53 g per charge.

- Second: they both are very light.
According to wikipedia (http://en.wikipedia.org/wiki/Fire_extinguisher#Installation), it should be like 9.1 kg and 2.3 kg.

Suggested settings:
big one:   60 charges, unchanged mass: 9100 g / 60 = 152 g per charge
small one: 12 charges, unchanged mass: 2300 g / 12 = 192 g per charge.

Balance:
Big fire extinguisher - better volume & weight "cost" per charge.
Small fire extinguisher - compact item, but weight "cost" is higher.


This is only my point of view, so any comments are welcome.