Resolution changing, insanity checks

-Constructor of CoreEngine now generates preset Tile data if doesn't
exist
-Added CoreEngine.changeResolution()
-Resolution change causes purple screen
-Added execCommand() for internal use
-Added Directory checks
-Added TerrarinLayer.nullTexture instead of a null tile, will not draw
if Tile Texture and nullTexture is null
-TerrainLayer.renderTarget now adjust to size change of screen
-removed BaseSprite.defaultTextureDir and defaultCorpseDir to be human
textures
-Added NLua libs to lib folder