Add craft station levels

[rubenwardy]

For example, furnaces could have the levels:

1. basic station - level 1 recipes only
2. station - level 2 recipes plus the recipes of the above level 1 station
3. alien station - level 3 recipes plus the recipes of the above level 2 station

or whatever.

Recipes would then be defined like:

crafting.register_craft({
    type = "furnace",
    level = 2,   -- can be made on Level 2 or 3 furnaces
    output = "default:iron_ingot",
    items = { "default:iron_ore" }
})

[rubenwardy]

0e6e3f0fe1bc0484daf505f82095667df181a347