CCRenderTexture added constructors without scaling

The this of the texture is scaled by CC_CONTENT_SCALE_FACTOR(). The
three new constructors where added to give possibility to also create
textures without automatic scale.
Merge pull request #2 from seagullua/CCRenderTextureExtenstion

CCRenderTexture added constructors without scaling
Merge pull request #3 from seagullua/develop-4enjoy

Develop 4enjoy