STYLE: add comments to SampleData class

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23646 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: add a testing clickAndDrag utility to the scripted module

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23647 3bd1e089-480b-0410-8dfb-8563597acbee