CCEffectColorChannelOffset - Add CGPoint versions of the offset properties

I should have used CGPoint all along instead of GLKVector2. Since this has been released I
can't change the existing interface so for now I'll add these new ones and deprecate the
GLKVector2 versions. This will all be updated in v4 to use only CGPoint for the offset values.
CCEffectsTest - Adds a second sprite color + effects test

This one tests all effects in both stacked and unstacked configurations and catches
a few effects that did not properly support sprite colors.
CCEffects - Sprite color fixes

Effects with non-default stitching requirements did not define any inputs and this
prevented them from handling sprite colors. Add custom input snippets that work
with the stitching requirements and correctly support sprite colors.
CCShader - Log shader source on link failure too

Previously we only did this on compilation failure.
Merge remote-tracking branch 'origin/develop' into develop
Merge pull request #1121 from thayerandrews/develop

CCEffects - Fix effect interaction with sprite colors