New nodelets to clip/create ROI

![screenshot from 2014-12-11 20 36 57](https://cloud.githubusercontent.com/assets/40454/5393480/d9c6f76c-8175-11e4-8463-f032c6be2541.png)

* AttentionClipper

  Create ROI from pose and camera info
* ROIClipper

  Clip image by specified ROI