Fix Examples/GUI/Qt/FourPaneViewer

QVTK does not exist anymore, use VTK_LIBRARIES instead.

vtkResliceImageViewer::SetInputConnection does not work,
and formerly emitted an error saying "Use SetInput" instead.

But there is no more SetInput, so the error message should
say "Use SetInputData"...

Updated the error message, and updated the example to avoid
the error message.

Change-Id: I64b6943dedc9956e7d6892d645356c2ffc87ad13
Merge topic 'fix-Examples-GUI-Qt-FourPaneViewer' into master

d7075681 Fix Examples/GUI/Qt/FourPaneViewer