Allow invocation of worklets to use vtkm::Id3
This allow invocation of worklets whose input domain is regular connectivity to be scheduled use the
DeviceAdapters Schedule(vtkm::Id3) method.
This is just the first step in having efficient 3d scheduling. The next step is to upgrade all the
vtkm::exec::arg to support Id3 index's for the load and store methods.
I would love somebody to suggest a better name for