BUG: #3524 check for valid images in Editor

This generates a warning for situations that are thought to be
invalid.  Since some tools may still be workable, we let the user
go ahead, but include some suggestions in the warnings about how
to fix the volumes.

http://na-mic.org/Bug/view.php?id=3524

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22772 3bd1e089-480b-0410-8dfb-8563597acbee