Avoid unecessary heavy template include in header. Not only could this
be avoided by restructuring the code but also avoid include bloat.
vtkDataSetSurfaceFilter.h is included in several places.

Use a different algorithm for computing surface for structured grids
with blanking. The new algorithm is about 10 times faster in fast mode
and 4 time faster in non-fast mode in my debug build for a 100^3 image data.
The new algorithm does not require accessing each input cell in fast mode
and hence the speedup.

Also making vtkDataSetSurfaceFilter::Delegate work for structured grids
i.e use vtkGeometryFilter internally, if requested.