Add new nodelet 'PlaneReasoner' to segment wall/ground

a nodelet which takes list of planes and classifies them into wall and ground.

Red planes are regarded as "ground" and green ones are regarded as "wall".

![screenshot from 2014-09-25 22 43 19](https://cloud.githubusercontent.com/assets/40454/4405327/f933c8b2-44b9-11e4-8bf3-dde6e53bcc10.png)