Add icons of liquids to blueprints icons set

[erikem]

Let player choose icons of liquids liquid when he creates a blueprint so he can accurately mark some of the liquid-realted bleuprints.

For example I have a factory setup that creates lubricant. On my blueprint I'd liek to see "chemical plant" icon and "lubricant" icon so I knwo in future what kind of chemical plant setup does this blueprint stand for. Alas currently icons of liquids are not available when creating a blueprint.

[bulldog98]

Yesterday I faced exactly this need, so I'm in favour of this.