Improve plane slice planner

[marip8]

Here is an example of using vtkCutter and vtkStripper to extract cut lines from meshes. We should update the plane slice raster to:

• Use the newer API for iterating over cell arrays
• Move the cutter outside of the for-loop since it has the ability to make more than one cut at a time

[marip8]

Closing; addressed by #350