Fix and enhance grid shapes in craft guide

Commit 043f608145 made shaped crafting
recipes display in a grid of the recipe's minimum bounding box,
but broke the use of a fixed 1x1 grid shape for cooking recipes.
This commit generalises the dynamic-grid-shape facility, putting the
craft type registration in charge.  This restores the correct shape for
cooking recipes.

Also change the logic for dynamic grid sizes for regular shaped and
shapeless crafting.  We'd like to always use a grid shape that is
reminiscent of a regular crafting grid, as a visual cue to the crafting
method.  But it's also nice to show smaller recipes in a smaller grid.
In the expectation that crafting grids will always be square, show the
recipe in the smallest square grid that will accommodate it.

api.lua

@@ -134,6 +134,13 @@ unified_inventory.register_craft_type("normal", {
 	description = "Crafting",
 	width = 3,
 	height = 3,
+	get_shaped_craft_width = function (craft) return craft.width end,
+	dynamic_display_size = function (craft)
+		local w = craft.width
+		local h = math.ceil(table.maxn(craft.items) / craft.width)
+		local g = w < h and h or w
+		return { width = g, height = g }
+	end,
 	uses_crafting_grid = true,
 })
 
@@ -142,6 +149,12 @@ unified_inventory.register_craft_type("shapeless", {
 	description = "Mixing",
 	width = 3,
 	height = 3,
+	dynamic_display_size = function (craft)
+		local maxn = table.maxn(craft.items)
+		local g = 1
+		while g*g < maxn do g = g + 1 end
+		return { width = g, height = g }
+	end,
 	uses_crafting_grid = true,
 })