The `CellMeasures` and `MeshQuality` filters had constructors that took the
metric that the filter should generate. However, this is different than the
iterface of the rest of the filters. To make the interface more consistent,
these filters now have a default (no argument) constructor, and the metric
to compute is selected via a method. This makes it more clear what is being
done.
In addition, the documentation for these two classes is updated.
Reenable the `vtkm::filter::CellMetric` class and
`vtkm::filter::MetricNames` static variable for backward compatibility.
(Both are of course marked deprecated.)
Also, adjust names in the new `vtkm::filter::mesh_info::CellMetric` to
conform with the rest of VTK-m style for scoped enums.
The testing files (even the headers) are not available if
`VTKm_ENABLE_TESTING` is off.
Mostly, the testing was used to generate example data sets. Instead,
change the examples to load data files.