Change to vtkStructuredGrid

[quantumsteve]

This issue was originally TRAC 11558

Utkarsh showed us how to use vtkStructuredGrid to avoid a memory copy. I temporarily removed it because the blanking arrays are not being processed by paraview at this time, but this is something we should work on early in the 3.5 release.

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Keywords: vates

[quantumsteve]

I created a trace of creating three slices of a MDHistoWorkspace to use as a benchmark. PV and Mantid build type is RelWithDebInfo. With ParaView, I also enabled OpenGL2 and tbb. Wall times to run the script were run twice and recorded below:

master (vtkUnstructuredGrid):

real 0m14.774s
user 0m11.824s
sys 0m2.550s

real 0m14.239s
user 0m11.764s
sys 0m2.509s

vtkStructuredGrid without blanking:

real 0m13.291s
user 0m11.773s
sys 0m1.500s

real 0m13.157s
user 0m11.704s
sys 0m1.493s

vtkStructuredGrid with blanking:

real 0m24.996s
user 0m23.436s
sys 0m1.549s

real 0m24.879s
user 0m23.366s
sys 0m1.540s

vtkStructuredGrid with vtkMDHWSignalArray:

real 0m25.654s
user 0m24.096s
sys 0m1.545s

real 0m24.852s
user 0m23.371s
sys 0m1.512s

vtkStructuredGrid with vtkMDHWSignalArray and vtkMDHWPointsArray:

real 0m42.802s
user 0m41.346s
sys 0m1.434s

real 0m42.507s
user 0m41.113s
sys 0m1.425s