Trajkovic

I add two new keypoints based on Trajkovic and Hedley operator.
First one is the original algorithm meant for comparison purposes.
Second one is part of my PhD dissertation and uses geometric criteria to find corners.
Both work on organized clouds only (for now).
![trajkovic_2d](https://f.cloud.github.com/assets/2897146/1754080/f46398f8-6648-11e3-9abf-be82166aea60.png)
![trajkovic_3d](https://f.cloud.github.com/assets/2897146/1754081/fbdc4ab2-6648-11e3-970b-9c23184c2999.png)