Get stitched effects working again

- Do not return the default CCEffect uniforms from CCEffectStack's extraFragment / VertexData methods.
- Restore the renderPassUpdate default block for super-simple effects like CCEffectTexture and CCEffectColorPulse.
  This allows these effects to not implement their own renderPassUpdate methods and still have things work.
- Re-enable setupEffectNodeTest in the effects test.
Set the position+color+texture shader in CCEffectNode's post-rendering composite phase

The original implementation of post-render composite phase didn't set the shader which meant
it was left as whatever the last effect's last render pass had set it to. This hadn't caused any visible
problems yet but it would have eventually and it also meant we were running a more expensive
shader than we needed to be.