CCEffects - Add color channel offset effect, fix effect clipping artifacts

- Add CCEffectColorChannelOffset which allows the red, green, and blue color channels to be offset from one another by independent 2D position vectors.
- Fix clipping of effects like blur that increase the size of the affected sprite. The user can now specify padding for their effects that increases the size of the submitted geometry without changing the visible size of the sprite image. Enlarging the geometry adds scratch space around the sprite image so blurs, blooms, and other effects do not get clipped by the geometry edges.
- Update the OSX project to include all the new effects.
Does it make sense to have separate independent/dependent texture read paths now that they are always dependent?