Introduce a few new nom::Renderer features

  - nom::Renderer
    * Rename set_viewport to set_logical_resolution
    * Introduce scale_factor method
    * Re-introduce set_viewport method using actual viewport call

  - examples/app
    * Update to reflect the API rename of set_viewport
Fix AnimatedSprite class

* examples/App: Add testing stub for AnimatedSprite class

  - AnimatedSprite
    * Rename method update to update_animation
    * Call SpriteBatch's update method in update_animation; intended
public access is the play method

  - SpriteBatch
    * Remove virtual declaration from update method

  - Cursor
    * Remove update method (this causes it to use SpriteBatch::update)
Fix SDL2 port of EventDispatcher class

* EventDispatcher: Change ERR check to match SDL2 API
* Input: Argument 'type' is now uint32 (from uint8) as per SDL2 API
Refactor joystick input subsystem for SDL2

Unfortunately, I don't have a second joystick laying around =(
Introduce debugging preprocessor for drag ’n’ drop events