Fixed Tank Rendering - Added Biomass

New textures for biomass. Biomass bucket is crude and not fully working.
Added MetaBucket

Fixed LiquidFuels bucket use with new class, MetaBucket. MetaBucket
extends MetaItems and handles just about everything needed to make a
bucket of placeable liquid.
Also renamed bucket_biomass.png to bucketBiomass.png.
Merge pull request #1 from LordBlackhole/LiquidFuelsDev

Liquid fuels dev