Massive refactoring to clean up models

* Tweak style of quantity label in output box to be more visible
* Move data files for all mods under a directory for the specific
  version of the mod
* Add a `silent` property to the base model to prevent models which
  shouldn't be observed from emitting events
* Change the term "itemSlug" to just "slug" across the board
* Change all models so that they don't require their parent in their
  constructors and so that they don't automatically add themselves to
  their parents lists
* Remove a bunch of unnecessary event triggering
* Tighten up access to various lists of children across all models
* Refactor the guts of the V2 parser into an abstract base class so
  it can be used for other parsers in the future
* Remove a number of unused methods

src/scripts/models/mod.coffee

@@ -6,6 +6,7 @@ All rights reserved.
 ###
 
 BaseModel = require './base_model'
+{Url}     = require '../constants'
 
 ########################################################################################################################
 
@@ -20,9 +21,5 @@ module.exports = class Mod extends BaseModel
 
     parse: (response)->
 
-    sync: (method, model, options={})->
-        if method isnt 'read' then throw new Error "Mod data can only be read, not #{method}d"
-        super method, model, options
-
     url: ->
-        return "/data/#{@slug}/mod.cg"
+        return Url.mod modSlug:@slug