Update vtkScalarsToColors classes to support color lookup table annotation.

This commit is based on VTK6 commit de162c7bc3371f.

As discussed on the VTK developer list, the associated VTK6 commit won't be
back-ported to VTK 5.10 release maintenance branch.
See http://vtk.1045678.n5.nabble.com/Possible-vtkScalarBarActor-improvement-tp5723463p5724200.html

Change-Id: I3fce1f25edbc38080fc1ec0555f95f937dde44e8