Add in the DataSetConverters from the contour branch.

Will need to add unstructured grid support.
Add support for UnstructuredGrids to DataSetConverters.h
Add in a simple dax accelerated threshold.
Add in accel threshold module.
Merge branch 'dax-contour' into enable-dax-modules
Enable the Streaming Contour Module.
Switch over to make the threshold as a paraview plugin.
Merge branch 'dax-threshold' into enable-dax-modules

Conflicts:
	CMakeLists.txt
	ModuleFactory.cxx
	dax/CMakeLists.txt
	dax/DataSetConverters.h
Update DataSetConverters to properly handle vtkSmartPointers.

The changes to add unstructured grid support, broke vtkSmartPointers
to vtkPolyData.
Show to user that they are using the accelerated threshold and contour.
Allow MatViz Module to change contour IsoValue.
Setup the streaming view behavior, now we can using streaming with matviz.
Double click on histogram now works with dax enabled.
Fix a bug where the vtkStreamingWorker wasn't caching HighLow computation.

We only need to compute the HighLow lookup the first time we run.
Setup a developer .plugin file for matviz
Document how to use the dax plugins in a matviz developer build.
Remove xml elements that have been deprecated.
Handle the use case of output of threshold from dax is zero cells.
Update the threshold to set the active scalars.
Improve the performance of appending subgrids to a single vtkPolyData.