Support Opacity for SpriteKit - set color with “colour” instead of “colo...

![screen shot 2014-07-29 at 10 20 06 am](https://cloud.githubusercontent.com/assets/5922890/3738144/89648278-173d-11e4-96f3-5c105110e9b5.png)

### Additions
Support Opacity for SpriteKit - set color with “colour” instead of “colorRGBA” and remove blend modes that are no longer supported. Working for:
- Image
- Color Node
- Color Gradient
- Finger Paint
## Todo
### Addressed (move tasks here once ready for review again)

### Outstanding (these tasks need developer attention)