Changes

Reworked Iron Engine Heat Mechanics

They cool down much faster, but use Coolant while doing so.
Additionally, they are affected by Biome temperature. Expect to need
more water/better Coolant in a desert for optimal operation. Ice Blocks
are also recommended.
 (commit: 48daafa)

Limit Coolant per tick rather Cooling per tick

Makes better Coolants more desirable because they can cool faster.
 (commit: f2f1828)