PDF textbooks: namespace JS variables for URLs

cms/static/js/models/textbook.js

@@ -39,7 +39,7 @@ CMS.Models.Textbook = Backbone.AssociatedModel.extend({
 });
 CMS.Collections.TextbookSet = Backbone.Collection.extend({
     model: CMS.Models.Textbook,
-    url: function() { return window.TEXTBOOK_URL; },
+    url: function() { return CMS.URL.TEXTBOOK; },
     initialize: function() {
         this.listenTo(this, "editOne", this.editOne);
     },

cms/static/js/views/textbook.js

@@ -259,7 +259,7 @@ CMS.Views.UploadDialog = Backbone.View.extend({
         var oldInput = this.$("input[type=file]").get(0);
         this.$el.html(this.template({
             shown: this.options.shown,
-            url: UPLOAD_ASSET_CALLBACK_URL,
+            url: CMS.URL.UPLOAD_ASSET,
             title: this.model.escape('title'),
             message: this.model.escape('message'),
             selectedFile: selectedFile,