sand group in silicon wafer recipe

[The4codeblocks]

implements/fixes #440

[OgelGames]

Works, but unified inventory doesn't show the correct quantity of sand for some reason:

I think it's a unified inventory problem though, because technic doesn't register the recipe any different for groups:

technic/technic/machines/register/recipes.lua

Lines 95 to 100 in 8e0a035

	unified_inventory.register_craft({
	type = recipe.method,
	output = output,
	items = table.copy(recipe.input),
	width = 0,
	})

[OgelGames]

minetest-mods/unified_inventory#283