ENH: Require external build of SlicerExecutionModel          The version of SEM source embedded here pre-dated an independant project from Slicer.  Now it is much easier to build SEM using a superbuild mechanism.
ENH: Require external build of SlicerExecutionModel
        
The version of SEM source embedded here pre-dated an
independant project from Slicer.  Now it is much
easier to build SEM using a superbuild mechanism.



juanprietob/DTIProcessToolkit,juanprietob/DTIProcessToolkit,NIRALUser/DTIProcessToolkit,NIRALUser/DTIProcessToolkit