ENH: #2761 Add CTCTDentalSurgery example

One click to get pre- and post- surgery scans, but the
logic API allows access to individual scans if desired.

http://na-mic.org/Bug/view.php?id=2761

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21952 3bd1e089-480b-0410-8dfb-8563597acbee