new tool: vol2sdp

small tool can be usefull to display segmentation results (classically from labels) in association with display3dImage. 
For instance:
![capture decran 2013-06-21 a 15 02 14](https://f.cloud.github.com/assets/772865/687182/48eb0330-da75-11e2-96ea-9f59bf8ac612.png)