adding oriented_gradient_node

I added node to calc 8 neighbor oriented gradient from input image.

![inimage](https://cloud.githubusercontent.com/assets/434105/3440640/bcde2e9c-00f9-11e4-8147-f9df0aafcf6d.jpg)
![orientedgradient](https://cloud.githubusercontent.com/assets/434105/3440641/bcdf5c72-00f9-11e4-81d2-75b0a6ebaf22.jpg)