Enable correction for left-rotated sprites.

CodeandWeb's TexturePacker produces right-rotated sprites which runs fine in Cocos2d-X. However, LibGDX's TexturePacker (https://github.com/libgdx/libgdx/wiki/Texture-packer) produces left-oriented sprites which Cocos2d-X renders as upside-down. This patch enables sprite loaders to set which specific rotation a sprite has for correnction.