ENH: Adding SimpleITK for Linux/Mac

This is a first pass at incorporating SimpleITK in to Slicer4 with ITK. It works on Linux/Mac, but not windows yet. There is a known way to make windows work, but that is going to take some time.

This set of patches will allow for a parallel set of development improvements to the Slicer/SimpleITK integration while the windows swig integration is worked out by more fully qualifed windows experts on the SimpleITK development team.

This enhancement will allow Hans and Sonia Pujol to work on identifying improvements to SimpleITK that would be useful in Slicer.