Fileutils perf improvements

Improves performance when creating `Node` and `Sprite` objects.

--> creates a common platform for apple: `CCFileutils` has only one file
--> prepends '/' to 'key' that are added in `TextureCache`
--> removed unused code
--> optimized `isAbsolutePath`
--> components in Node uses lazy alloc

Overall:
Creating 500 empty sprites went from 4.4s to 0.6s
Creating 500 non empty sprites went from 1.6s to 0.8