Moved AppDelegate methods into modules

This allows the gem to work with other gems that require you subclassing for your `AppDelegate`, or if you just have some code personally that does that.  Currently, the `AppDelegate` class was just a subclass of `Object` and defining that in your application would lead to a compiler error.

```ruby
class AppDelegate < ProMotion::AppDelegate

  include Nitron::AppDelegateCoreData
  include Nitron::AppDelegateStoryboard

  def on_init
    # ProMotion gem code here
  end

end
```