Better localStorage support detection.

In IE9 when file is opened from local filesystem the localStorage
property of window exists, but is undefined.

Author: nene

template/app/LocalStore.js

@@ -13,7 +13,7 @@ Ext.define("Docs.LocalStore", {
      * localStorage available.
      */
     init: function() {
-        this.localStorage = ('localStorage' in window && window['localStorage'] !== null);
+        this.localStorage = !!window['localStorage'];
         this.store = Ext.getStore(this.storeName);
 
         if (this.localStorage) {

template/app/model/Setting.js

@@ -5,7 +5,7 @@ Ext.define('Docs.model.Setting', {
     fields: ['id', 'key', 'value'],
     extend: 'Ext.data.Model',
     proxy: {
-        type: ('localStorage' in window && window['localStorage'] !== null) ? 'localstorage' : 'memory',
+        type: window['localStorage'] ? 'localstorage' : 'memory',
         id: Docs.localStorageDb + '-settings'
     }
 });