Adding some graphics to the 2D Platforming sample code from  http://www.nandnor.net/?p=64

Material
    Original source code:   http://www.nandnor.net/code/platformer/platform.txt
    Art Assets from Kenney's donation pack: http://kenney.itch.io/kenney-donation

Work order:
    - Refactor the single file code into manageable modules
    - Replace rectangles with dirty terrain
    - Random map generation