ENH: Add SHIFT support to change file type to checked files.

Holding the shift key when changing the file type changes the other checked
files of same type to the new file type.
Closes #3109

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22204 3bd1e089-480b-0410-8dfb-8563597acbee