Reverts Cael's retard flailing.  Do not fuck with zone sharing ratios...  Also: Fixed fire.


![Untitled](https://f.cloud.github.com/assets/1243563/338096/cd9b9f6a-9d01-11e2-89ad-a12e7fd58a5d.png)
...unless you know what you are doing, as air movement then becomes quite chaotic and derpy.  Should fix some issues with ZAS.

Makes the maximum amount of gases shared between zones to be 42% of the gases in both zones, scaling with how large the connection between the zones are.

If you wish to speed up the exchange of air, adjust the values in the sharing_lookup_table.  Do not exceed a value of 0.5
Current settings: 1 tile: 12%; 2 tiles: 22%; 3 tiles: 30%; 4 tiles: 36%; 5 tiles: 40%; 6 tiles: 42%