vtkStaticCellLinks has been rewritten using std::atomic and vtkSMPTools for
an ~10x speed improvement. Some clean up and improvements to the API, including
classes that use cell links were also made. An additional construct is the
notion of a dataset being "editable". That is, after a dataset is constructed,
it is assumed non-editable if no further modifications to the geometry and topology
are made. This allows the use of static locators and cell links classes. If editable,
then the old vtkCellLinks and vtkPointLocators are used, and certain editing methods
in the dataset API are allowed.