Performance enhancement to JSON dep scanning

When the templates are scanned the results are not cached to the
dependencies don't need to be recomputed for each json.

Change-Id: I1a1fca9772d7dd62cd8d70e022ff8d63cafe365a
Merge topic 'SIMPLEITK-392_ImproveJSONScanning' into next

06c1437 Performance enhancement to JSON dep scanning