This issue is here to track cleanup of the BlockIronTank.java class. Its more of a reminder to myself of what direction to take than a concrete TODO list.

• Remove overridden getIconAbsolute() required logic should be covered by super now
• Make IronTankType type public final, remove int tankVolume and String blockName (use properties from type)
• Remove getInternalName() method, shouldn't be necessary
• Remove registerBlockIcons() ... testing needed to make sure this doesn't break anything
• Refactor class as BlockExtendedTank