Simplify Testing/Cxx/CMakeLists.txt using SEM_LAUNCH_COMMAND

This variable has been introduced in Slicer r21737.
See http://viewvc.slicer.org/viewvc.cgi/Slicer4?view=revision&revision=21737
Fix test by associating the appropriate inputs and baseline

Fixes #1
Merge pull request #2 from jcfr/fix-test-using-valid-inputs-and-baseline

Fix test using valid inputs and baseline