vtkStreamTracer: Improve performance and correctness

vtkStreamTracer has be enabled to run using SMP when 1 MPI is core is used. Moreover, FindCell operation using both vtkCellLocatorStrategy and vtkClosestPointStrategy has been improved performance-wise. Also, vtkFindCellStrategy has a FindClosestPointWithinRadius function which both vtkCellLocatorStrategy and vtkClosestPointStrategy implement. vtkCellLocatorStrategy does it using a CellLocator, and vtkClosestPointStrategy does it using the approach previously existing in vtkAbstractInterpolatedVelocityField's FindCellAndUpdate. Similarly, since now both vtkInterpolatedVelocityField and vtkCellLocatorInterpolatedVelocityField should be able to perform SnapPointOnCell , and they were almost identical (except the used strategy), their implementation has been moved to their parent class vtkCompositeInterpolatedVelocityField. Furthermore, vtkAbstractInterpolatedVelocityField's FindCellAndUpdate has been carefully optimized to perform the minimum number of EvaluatePosition/EvaluateLocation/GetCell. Finally, the quality when the SurfaceDataSet is enabled has been improved significantly.

cc: @will.schroeder (in case you want to see the improvements)