Code review of vtkStructuredGrid.cxx, notably deprecated GetDimensions
- replaced all uses of the GetDimensions() that returns an inner pointer with the GetDimensions() that copies into a given buffer. This is more thread safe.
- made a few array parameters VTK_FUTURE_CONST
- moved some variable declarations to be closer to assignment/use
- renamed some dim variables to dims, since there are many
- altered GetCell(int i, int j, int k) to no longer access this->Dimensions before updating this->Dimensions via the now-deprecated GetDimensions()
- altered GetCell(vtkIdType cellId, vtkGenericCell* cell) to return early if there are no points (instead of just calling vtkErrorMacro)