Complete refactoring to move Recipes into Items

* Changed "version" to "dataVersion" in data format
* Changed the "modName" and "modVersion" fields on the ModVersion
  class to remove the "mod" prefix and changed the data format to
  match
* Change the Stack class to use the itemSlug instead of the item
  itself
* Update the ModVersion and ModPack classes to include methods for
  recording a correspondence between slugs and names. Update code
  which displays items from stacks to use these methods to determine
  display names.
* Add a reference from Recipe back to the item it creates

src/scripts/models/item.coffee

@@ -27,8 +27,8 @@ module.exports = class Item extends BaseModel
     # Public Methods ###############################################################################
 
     addRecipe: (recipe)->
-        output = recipe.output[0].item
-        if output isnt this then throw new Error "invalid recipe for #{@name} because it makes a #{output.name}"
+        slug = recipe.output[0].itemSlug
+        if slug isnt @slug then throw new Error "invalid recipe for #{@slug} because it makes a #{slug}"
 
         @recipes.push recipe