runTimePostProcessing: use existing cutting planes

Cross ref : EP#868

@andy @mark

mentioned in issue #1125 (closed)

mentioned in commit 78430150

mentioned in commit 0cbb07f5

mentioned in issue #1126

Add direct support for vtp surfaces

mentioned in commit 98fb25e7

@Prashant - This should now handle vtp properly for current and future. I tested (ellipse tutorial) using surfaceMeshTriangulate to extract the boundary surface.

Another point for checking is the dummy runTimePostProcessing. If you have a system without VTK or ParaView for compilation, it should now create a stub for the functionObject. If you use runTimePP and don't have the proper VTK libs at compile time, it should now just complaint and toss out the function object, but not crash anything.