CCNode perf improvements

AffineTransforms uses a const global variable for the `IDENTITY`
`removeObject` only seeks the index once

Signed-off-by: Ricardo Quesada <ricardoquesada@gmail.com>
API compliant with cocos2d-x best practices

Uses `int` instead of `unsigned int` as described in the cocos2d-x best practices

Signed-off-by: Ricardo Quesada <ricardoquesada@gmail.com>
Little performance improvements

Uses `AffineTransform::IDENTITY`

Signed-off-by: Ricardo Quesada <ricardoquesada@gmail.com>
fixes possible crash when using `SpriteFrameCache`

the returned dictionary was double-released. ouch.

Signed-off-by: Ricardo Quesada <ricardoquesada@gmail.com>