add new nodelet: BorderEstimator

add new nodelet to estimate border based on range image.

* white: border
* green: shadow
* red: veil

![screenshot_from_2014-08-26 16 19 24](https://cloud.githubusercontent.com/assets/40454/4041110/40c3c2bc-2cf1-11e4-84da-4d749f4bec82.png)