default value for Locstor.get


Sample usage:
```javascript
//app.userSettings previously defined. 
Object.defineProperty(app.userSettings, 'notificationsEnabled', {
    get: function () { return Locstor.get('notificationsEnabled', false); },
    set: function (v) { Locstor.set('notificationsEnabled', v); }
});
```
This way if the code attempts to get the value of a undefined local storage object, a default value can be returned.