Mistake in naming of sprite node constructors

[Manuel M T Chakravarty]

• All the spriteWithXYZ functions actually ought to be called spriteNodeWithXYZ.
• Rename, but keep the old version (deprecated) around for a while to ease the transition. Maybe we should keep them and introduce similar short forms for the other nodes...
• Add support for normal maps to sprites and also add light nodes (and the needed functionality on textures). Moved to #12.