Add DTIAtlasBuilder extension See issue #167

DTIAtlasBuilder is a tool to create an DTI atlas image from several DTI images : https://www.nitrc.org/projects/dtiatlasbuilder

Your can find the source code here : https://github.com/NIRALUser/DTIAtlasBuilder
A tutorial is available on NITRC : https://www.nitrc.org/docman/view.php/636/1189/DTIAtlasBuilder_Tutorial.pdf

The tool is a GUI where the user can add his DTI images, and set several options. Then the program will write a python script and run it to call external tools to process the data and create the Atlas.