Update DTIProcess extension

The extension has been entirely repackage to compile and package properly. The cmake flags are now given to the sub project through superbuild. The cmake* files follow the same format as the one provided by Slicer and DTIPrep.
Merge pull request #165 from booboo69500/update-DTIProcess

The extension has been entirely repackage to compile and package properly. The cmake flags are now given to the sub project through superbuild. The cmake* files follow the same format as the one provided by Slicer and DTIPrep.